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<title data-rh="true">SLI Compass: Fidelity and Granulairty - Alex Ewerlöf Notes</title>
<meta data-rh="true" name="theme-color" content="#001426"/><meta data-rh="true" property="og:type" content="article"/><meta data-rh="true" property="og:title" content="SLI Compass: Fidelity and Granulairty"/><meta data-rh="true" name="twitter:title" content="SLI Compass: Fidelity and Granulairty"/><meta data-rh="true" name="description" content="A Mental Model to Assess Existing SLIs and Evaluate New Ones. We discuss 2 dimension: fidelity shows how closely your SLI is measuring the user experience, granularity shows how many parameter are measured by your SLI.
Learn how to quickly evaluate existing SLIs and choose new ones based on their cost, complexity, and signal-to-noise ratio."/><meta data-rh="true" property="og:description" content="A Mental Model to Assess Existing SLIs and Evaluate New Ones. We discuss 2 dimension: fidelity shows how closely your SLI is measuring the user experience, granularity shows how many parameter are measured by your SLI"/><meta data-rh="true" name="twitter:description" content="A Mental Model to Assess Existing SLIs and Evaluate New Ones. We discuss 2 dimension: fidelity shows how closely your SLI is measuring the user experience, granularity shows how many parameter are measured by your SLI"/><meta data-rh="true" property="og:image" content="https://substackcdn.com/image/fetch/$s_!5TKM!,w_1200,h_675,c_fill,f_jpg,q_auto:good,fl_progressive:steep,g_auto/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png"/><meta data-rh="true" name="twitter:image" content="https://substackcdn.com/image/fetch/$s_!Gmcd!,f_auto,q_auto:best,fl_progressive:steep/https%3A%2F%2Falexewerlof.substack.com%2Fapi%2Fv1%2Fpost_preview%2F170275899%2Ftwitter.jpg%3Fversion%3D4"/><meta data-rh="true" name="twitter:card" content="summary_large_image"/><meta data-rh="true" property="article:modified_time" content="2025-08-27T12:13:29.544Z"/>
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We discuss 2 dimension: fidelity shows how closely your SLI is measuring the user experience, granularity shows how many parameter are measured by your SLI.\nLearn how to quickly evaluate existing SLIs and choose new ones based on their cost, complexity, and signal-to-noise ratio.","image":[{"@type":"ImageObject","url":"https://substackcdn.com/image/fetch/$s_!5TKM!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png"}],"datePublished":"2025-08-08T11:14:03+00:00","dateModified":"2025-08-08T11:14:03+00:00","isAccessibleForFree":true,"author":[{"@type":"Person","name":"Alex Ewerl\u00F6f","url":"https://substack.com/@alexewerlof","description":"Writes about technical leadership, growth mindset, and system reliability engineering. Senior Staff Engineer, MSc Systems Engineering from KTH, Stockholmer, dad, amateur artist. 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class="label">Share</div></button></div></div></div></div><div class="visibility-check"></div><div><div class="dt-post-body"><div class="available-content"><div dir="auto" class="body markup"><p><a href="https://blog.alexewerlof.com/p/sli">Service Level Indicator</a><span> (SLIs) is a fundamental concept in reliability engineering. Done right, it quantifies the level of service from the consumer’s point of view in line with the business objectives.</span></p><p>However, different SLIs have different signal to noise ratio and ROI (return on investment).</p><p>This article introduces SLI Compass, a 2D mental model to help you:</p><ul><li><p>Quickly assess the signal/noise ratio of existing SLIs</p></li><li><p>Evaluate SLIs based on their cost and complexity</p></li><li><p>Set a direction for improving the quality of existing SLIs at a reasonable ROI</p></li></ul><p>The goal is to help senior engineers, technical and engineering leaders to pick the right SLI based on product maturity, budget, timing, and usage patterns.</p><div data-component-name="SubscribeWidget" class="subscribe-widget"><div class="pencraft pc-display-flex pc-justifyContent-center pc-reset"><div class="container-IpPqBD"><form action="/api/v1/free?nojs=true" method="post" novalidate class="form form-M5sC90"><input type="hidden" name="first_url" value/><input type="hidden" name="first_referrer" value/><input type="hidden" name="current_url"/><input type="hidden" name="current_referrer"/><input type="hidden" name="first_session_url" value/><input type="hidden" name="first_session_referrer" value/><input type="hidden" name="referral_code"/><input type="hidden" name="source" value="subscribe-widget"/><input type="hidden" name="referring_pub_id"/><input type="hidden" name="additional_referring_pub_ids"/><input type="hidden" name="source_post_id" value="170275899"/><div class="sideBySideWrap-vGXrwP"><div class="emailInputWrapper-QlA86j"><div class="pencraft pc-display-flex pc-minWidth-0 pc-position-relative pc-reset flex-auto-j3S2WA"><input name="email" placeholder="Type your email..." type="email" class="pencraft emailInput-OkIMeB input-y4v6N4 inputText-pV_yWb"/></div></div><button tabindex="0" type="submit" disabled class="pencraft pc-reset pencraft rightButton primary subscribe-btn button-VFSdkv buttonBase-GK1x3M"><span class="button-text ">Subscribe</span></button></div><div id="error-container"></div></form></div></div></div><h1 class="header-anchor-post">Categorizing SLIs<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§categorizing-slis" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/categorizing-slis" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h1><p>I’ve gone through hundreds of architectures with tens of teams over the years both at my companies and external clients.</p><p>In my experience the most common SLIs are:</p><ul><li><p><strong>Availability:</strong><span> is the service available to the consumer and can it be used for their tasks? This is by far the most common SLI except for async services like queues where other metrics make more sense.</span></p></li><li><p><strong>Latency:</strong><span> how long does it take to interact with the service? This is very common for user-facing services, or services that have a time-critical consumption like Frontend, API, Databases, CDN, queued workload processing, etc.</span></p></li><li><p><strong>Success rate:</strong><span> how often do consumers manage to fulfill their task? This is common with transactional services like REST APIs, user journeys, or even queued workload (e.g. dead-letter queue).</span></p></li><li><p><strong>Efficiency:</strong><span> is the service operating with the right trade-offs that makes business sense? For example: are we using too much GPU for free user requests? Is the Cache being utilized? Are queued work being processed? etc.</span></p></li></ul><p>There are also other niche metrics like correctness, freshness, relevance, etc.</p><p>All SLIs can be mapped in a 2D axis:</p><ul><li><p><strong>Fidelity:</strong><span> how closely does the SLI represent the consumer experience?</span></p></li><li><p><strong>Granularity:</strong><span> how many variables and parameters are aggregated in a single data point?</span></p></li></ul><p>We can combine these two dimensions to get a powerful but familiar quadrant model.</p><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!5TKM!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!5TKM!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 424w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 848w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 1272w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!5TKM!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png" width="1062" height="1061" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1061,&quot;width&quot;:1062,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:1800473,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!5TKM!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 424w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 848w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 1272w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p>As we will see, a single category of SLIs like availability or latency, can fit into any of those 4 quadrants.</p><h1 class="header-anchor-post">The two dimensions<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§the-two-dimensions" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/the-two-dimensions" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h1><h2 class="header-anchor-post">1. Fidelity: how closely does the SLI represent the consumer experience?<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§1-fidelity-how-closely-does-the-sli-represent-the-consumer-experience" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/1-fidelity-how-closely-does-the-sli-represent-the-consumer-experience" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h2><p><span>SLI </span><strong>Fidelity</strong><span>, refers to how the data, or telemetry, is generated and how accurately it represents the consumer’s experience of the service.</span></p><ul><li><p><strong>Synthetic metrics</strong><span> use artificial, fake, or simulated loads. A common example is a tool that pings an endpoint every minute to gather data about latency or availability. This check ensures the endpoint is responsive.</span></p></li><li><p><strong>Organic metrics</strong><span> gather data from consumers actually using the service. For example, we can gather availability and latency data from API gateway that exposes a service externally. This is a more precise way to measure service level.</span></p></li></ul><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!Y06S!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!Y06S!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!Y06S!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png" width="1063" height="1062" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/383ec274-9944-4227-8403-36f127899717_1063x1062.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1062,&quot;width&quot;:1063,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:431888,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!Y06S!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p>Organic metrics are more realistic. They map directly to what's happening in production.</p><p>However, they can be harder to measure. For high-traffic services, they can generate massive amounts of data. This requires a more robust and costly monitoring infrastructure.</p><p><span>For low-traffic services, there may not be enough organic load to for the SLI formula to work correctly. That’s because SLI status (also known as </span><a href="https://blog.alexewerlof.com/p/sls">SLS</a><span>), is a percentage based.</span></p><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!Hf1l!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!Hf1l!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 424w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 848w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 1272w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!Hf1l!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png" width="1060" height="601" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:601,&quot;width&quot;:1060,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:67719,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!Hf1l!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 424w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 848w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 1272w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p>For example, if a service receives 50 request per months, it is not reasonable to expect a success rate of 99% because a single failure in that period reduces the service level status (SLS) to 98%. In this case, one solution can be to use synthetic metric.</p><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!aIfH!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!aIfH!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 424w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 848w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 1272w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!aIfH!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png" width="1060" height="695" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/ac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:695,&quot;width&quot;:1060,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:58981,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!aIfH!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 424w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 848w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 1272w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p>Synthetic load can potentially skew product metrics. For example, if the product is measuring MAU (monthly active users), it’s important to have a way to distinguish fake users (synthetic) from the real ones. Otherwise, wrong data can lead to wrong decisions.</p><h2 class="header-anchor-post">2. Granularity: How many variables are aggregated by the SLI data points?<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§2-granularity-how-many-variables-are-aggregated-by-the-sli-data-points" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/2-granularity-how-many-variables-are-aggregated-by-the-sli-data-points" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h2><p><span>Let's look at the second dimension of SLIs: their </span><strong>granularity</strong><span>, which refers to the number of parameters or variables being tested to quantify the level of the service.</span></p><ul><li><p><strong>Simple: </strong><span>measure only one thing. For example, a simple metric might check if an endpoint returns a </span><code>200</code><span> HTTP status code (for availability) or if a single API call's latency is below a threshold. This tells you the basic health of one component. It acts as a basic </span><strong>proxy</strong><span> for overall service health. It doesn't say if the service is actually useful to the consumer's complete task.</span></p></li><li><p><strong>Complex:</strong><span> measure multipel things. This tells a richer story about the </span><strong>consumer journey</strong><span> or complex system behavior. A high-fidelity metric could track the success rate and latency of all steps in a critical user purchase flow. It ensures they are working as expected.</span></p></li></ul><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!lnLL!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!lnLL!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!lnLL!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png" width="1063" height="1062" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1062,&quot;width&quot;:1063,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:435243,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!lnLL!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p><span>Complex SLIs aggregate multiple variables. For example, instead of pinging the home page (simple), we run a </span><a href="https://playwright.dev/">Playwright</a><span> script that traverses a user journey to identify any broken step.</span></p><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!bkoT!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!bkoT!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 424w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 848w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 1272w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!bkoT!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png" width="1059" height="565" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:565,&quot;width&quot;:1059,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:53520,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!bkoT!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 424w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 848w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 1272w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p>Complex SLIs can be more costly to maintain.</p><p>They might also introduce a lag in flagging an incident because they have to wait to get data for all variables. This is because they require more data processing and aggregation.</p><p>However, complex SLIs provide a higher-quality signal because they reflect a user's experience more accurately.</p><p>On the flipside, it can be harder to reason about the complex SLIs due to aggregation: if there’s a failure, what did exactly fail?</p><p>To answer that question, we need to store more data, which adds to the cost of complex SLIs.</p><p>One caveat for complex SLIs is the ownership of different variables. Most metrics aggregate multiple variables.</p><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!mbrn!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!mbrn!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 424w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 848w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 1272w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!mbrn!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png" width="1035" height="912" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:912,&quot;width&quot;:1035,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:77498,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!mbrn!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 424w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 848w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 1272w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p>Ideally you want each data point to only aggregate variables that are within the control of one team. Because when the metric shows a service degradation or disruption, it is easy to reason about who owns the service and should receive an alert to fix it.</p><h2 class="header-anchor-post">Putting it together<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§putting-it-together" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/putting-it-together" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h2><p>Putting everything together, we get this 2D Compass:</p><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!v_yw!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!v_yw!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!v_yw!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png" width="1063" height="1062" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1062,&quot;width&quot;:1063,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:474836,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!v_yw!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><h1 class="header-anchor-post">Examples<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§examples" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/examples" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h1><p>Availability is the most common SLIs. At the basic level it’s an answer to this question:</p><blockquote><p>Is the service exposed to the consumer?</p></blockquote><p>However, a better question can be:</p><blockquote><p>Can the consumer use the service to do their tasks and achieve their goals?</p></blockquote><p>The difference is subtle but important:</p><ul><li><p><span>The former is aligned with the </span><strong>service provider</strong><span>’s basic commitment and is usually easier to measure.</span></p></li><li><p><span>The latter is aligned with the </span><strong>service consumer</strong><span>’s expectation and is typically harder to measure.</span></p></li></ul><div data-component-name="DigestPostEmbed" class="digestPostEmbed-flwiST"><a href="https://blog.alexewerlof.com/p/service-level-terminology" rel="noopener" target="_blank"><div class="pencraft pc-display-flex pc-gap-16 pc-reset"><div style="width:70px;height:70px;" class="pencraft pc-reset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!MlI7!,w_140,h_140,c_fill,f_webp,q_auto:good,fl_progressive:steep,g_auto/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F5bb74595-f0d9-4d19-9a4c-23d596b721a8_1010x1122.png"/><img src="https://substackcdn.com/image/fetch/$s_!MlI7!,w_140,h_140,c_fill,f_auto,q_auto:good,fl_progressive:steep,g_auto/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F5bb74595-f0d9-4d19-9a4c-23d596b721a8_1010x1122.png" sizes="100vw" alt="Service Level Terminology" width="140" height="140" class="img-OACg1c smSquare-NGbPBa pencraft pc-reset"/></picture></div><div class="pencraft pc-display-flex pc-flexDirection-column pc-reset"><h4 class="pencraft pc-reset color-pub-primary-text-NyXPlw line-height-24-jnGwiv font-display-nhmvtD size-20-P_cSRT weight-bold-DmI9lw reset-IxiVJZ">Service Level Terminology</h4><div class="pencraft pc-display-flex pc-gap-4 pc-alignItems-center pc-reset"><div class="pencraft pc-reset color-pub-secondary-text-hGQ02T line-height-20-t4M0El font-meta-MWBumP size-11-NuY2Zx weight-medium-fw81nC transform-uppercase-yKDgcq reset-IxiVJZ meta-EgzBVA"><a href="https://substack.com/profile/87732486-alex-ewerlof" class="inheritColor-WetTGJ">Alex Ewerlöf</a></div><div class="pencraft pc-reset color-pub-secondary-text-hGQ02T reset-IxiVJZ">·</div><div class="pencraft pc-reset color-pub-secondary-text-hGQ02T line-height-20-t4M0El font-meta-MWBumP size-11-NuY2Zx weight-medium-fw81nC transform-uppercase-yKDgcq reset-IxiVJZ meta-EgzBVA">October 25, 2024</div></div><div class="pencraft pc-display-flex pc-gap-16 pc-paddingTop-0 pc-paddingBottom-0 pc-alignItems-center pc-reset"><a href="https://blog.alexewerlof.com/p/service-level-terminology" class="pencraft pc-reset align-center-y7ZD4w line-height-20-t4M0El font-text-qe4AeH size-13-hZTUKr weight-medium-fw81nC reset-IxiVJZ"><div class="pencraft pc-display-flex pc-gap-8 pc-alignItems-center pc-reset link-HREYZo"><span class="pencraft pc-reset color-accent-BVX_7M line-height-20-t4M0El font-text-qe4AeH size-14-MLPa7j weight-semibold-uqA4FV reset-IxiVJZ">Read full story</span><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-arrow-right"><path d="M5 12h14"></path><path d="m12 5 7 7-7 7"></path></svg></div></a></div></div></div></a></div><p>How can we measure availability for an API server?</p><ol><li><p><strong>Simple &amp; Synthetic:</strong><span> ping the health endpoint every minute and calculate the percentage of successful pings in a </span><a href="https://blog.alexewerlof.com/p/compliance-period">period</a></p></li><li><p><strong>Simple &amp; Organic:</strong><span> count the number of minutes where the API endpoint could handle valid requests (i.e. with valid auth header) in a </span><a href="https://blog.alexewerlof.com/p/compliance-period">period</a></p></li><li><p><strong>Complex &amp; Synthetic:</strong><span> use synthetic monitoring to test that the critical user flow (e.g. a purchase journey) works and calculate the successful execution percentage</span></p></li><li><p><strong>Complex &amp; Organic:</strong><span> use the RUM (real-user monitoring) data to identify any broken user journeys and calculate successful user sessions</span></p></li></ol><p>Let’s do this exercise for latency, which is the second most common SLI:</p><ol><li><p><strong>Simple &amp; Synthetic:</strong><span> Measure the response time of a periodic </span><code>GET</code><span> request to a predesignated endpoint (i.e. </span><code>www.example.com/api/health</code><span>) and calculate the </span><a href="https://blog.alexewerlof.com/p/percentile">P99 percentile</a><span> over a </span><a href="https://blog.alexewerlof.com/p/compliance-period">period</a><span>.</span></p></li><li><p><strong>Simple &amp; Organic:</strong><span> Calculate the </span><a href="https://blog.alexewerlof.com/p/percentile">P99 percentile</a><span> latency for all successful API requests from real users as measured at the API gateway.</span></p></li><li><p><strong>Complex &amp; Synthetic:</strong><span> periodically simulate a complete user transaction (e.g., login, search, add to cart, checkout) and measure the end-to-end response time.</span></p></li><li><p><strong>Complex &amp; Organic:</strong><span> Analyze Real User Monitoring (RUM) data to track the full-page load time, including all resource fetches and rendering, for critical user journeys.</span></p></li></ol><h1 class="header-anchor-post">Signal to noise ratio<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§signal-to-noise-ratio" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/signal-to-noise-ratio" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h1><p><span>Good SLIs are worthy of being on-call for because they indicate service </span><a href="https://blog.alexewerlof.com/p/service-degradation-vs-disruption">degradation or disruption</a><span> with high accuracy. Even if there is no 24/7 on-call rotation, this is still a good mindset to evaluate an SLI:</span></p><ol><li><p><strong>Does this SLI help us get notified when there is an incident?</strong><br/><span>(incident in this context is any failure that threatens the business objective)</span></p></li><li><p><strong>Does each anomaly in this SLI indicate an incident?</strong><br/><span>(no false positive or false negative)</span></p></li></ol><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!bkSH!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!bkSH!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 424w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 848w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 1272w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!bkSH!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png" width="1038" height="992" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:992,&quot;width&quot;:1038,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:81852,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!bkSH!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 424w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 848w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 1272w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p>SLI is the basis for a solid ownership implementation:</p><ul><li><p>SLI measures the level of service from consumer’s perspective</p></li><li><p><a href="https://blog.alexewerlof.com/p/slo">SLO</a><span> helps:</span></p><ul><li><p>The stakeholders set expectations on the service owner</p></li><li><p>The service owner communicate their commitment to service consumers</p></li></ul></li><li><p>Alerts: tie that expectation or commitment to responsibility and accountability</p></li></ul><p>Poor SLIs lead to broken ownership.</p><div data-component-name="DigestPostEmbed" class="digestPostEmbed-flwiST"><a href="https://blog.alexewerlof.com/p/broken-ownership" rel="noopener" target="_blank"><div class="pencraft pc-display-flex pc-gap-16 pc-reset"><div style="width:70px;height:70px;" class="pencraft pc-reset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!E-8i!,w_140,h_140,c_fill,f_webp,q_auto:good,fl_progressive:steep,g_auto/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F72091ddc-6191-4ccb-8d06-15a7edbed199_1012x964.png"/><img src="https://substackcdn.com/image/fetch/$s_!E-8i!,w_140,h_140,c_fill,f_auto,q_auto:good,fl_progressive:steep,g_auto/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F72091ddc-6191-4ccb-8d06-15a7edbed199_1012x964.png" sizes="100vw" alt="6 Archetypes of Broken Ownership" width="140" height="140" class="img-OACg1c smSquare-NGbPBa pencraft pc-reset"/></picture></div><div class="pencraft pc-display-flex pc-flexDirection-column pc-reset"><h4 class="pencraft pc-reset color-pub-primary-text-NyXPlw line-height-24-jnGwiv font-display-nhmvtD size-20-P_cSRT weight-bold-DmI9lw reset-IxiVJZ">6 Archetypes of Broken Ownership</h4><div class="pencraft pc-display-flex pc-gap-4 pc-alignItems-center pc-reset"><div class="pencraft pc-reset color-pub-secondary-text-hGQ02T line-height-20-t4M0El font-meta-MWBumP size-11-NuY2Zx weight-medium-fw81nC transform-uppercase-yKDgcq reset-IxiVJZ meta-EgzBVA"><a href="https://substack.com/profile/87732486-alex-ewerlof" class="inheritColor-WetTGJ">Alex Ewerlöf</a></div><div class="pencraft pc-reset color-pub-secondary-text-hGQ02T reset-IxiVJZ">·</div><div class="pencraft pc-reset color-pub-secondary-text-hGQ02T line-height-20-t4M0El font-meta-MWBumP size-11-NuY2Zx weight-medium-fw81nC transform-uppercase-yKDgcq reset-IxiVJZ meta-EgzBVA">August 1, 2023</div></div><div class="pencraft pc-display-flex pc-gap-16 pc-paddingTop-0 pc-paddingBottom-0 pc-alignItems-center pc-reset"><a href="https://blog.alexewerlof.com/p/broken-ownership" class="pencraft pc-reset align-center-y7ZD4w line-height-20-t4M0El font-text-qe4AeH size-13-hZTUKr weight-medium-fw81nC reset-IxiVJZ"><div class="pencraft pc-display-flex pc-gap-8 pc-alignItems-center pc-reset link-HREYZo"><span class="pencraft pc-reset color-accent-BVX_7M line-height-20-t4M0El font-text-qe4AeH size-14-MLPa7j weight-semibold-uqA4FV reset-IxiVJZ">Read full story</span><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-arrow-right"><path d="M5 12h14"></path><path d="m12 5 7 7-7 7"></path></svg></div></a></div></div></div></a></div><h1 class="header-anchor-post">Pro Tips: When and how to use the SLI compass?<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§pro-tips-when-and-how-to-use-the-sli-compass" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/pro-tips-when-and-how-to-use-the-sli-compass" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h1><p>Broadly speaking there are 3 categories of use cases for SLI compass:</p><ol><li><p><strong>Evaluation:</strong><span> Assess the signal quality of an SLI and its effectiveness in implementing </span><a href="https://blog.alexewerlof.com/p/you-build-it-you-own-it">full ownership</a><span> through alerts.</span></p></li><li><p><strong>Investment:</strong><span> Estimate the </span><a href="https://blog.alexewerlof.com/p/tech-bet">ROI (return on investment)</a><span> of an existing or new SLI</span></p></li><li><p><strong>Evolution:</strong><span> motivate improving how tech health is measured using </span><a href="https://blog.alexewerlof.com/p/sli">SLI</a><span> and </span><a href="https://blog.alexewerlof.com/p/premature-optimization">optimized</a><span> towards an </span><a href="https://blog.alexewerlof.com/p/slo">SLO</a></p></li></ol><p>For example, when Service Levels (as a concept) is new to an organization, you want to start small and easy. A simple synthetic check like pinging the home page every minute is a pretty good start.</p><p>In fact, this is so common that there’s a whole product sector doing exactly that: Pingdom, UptimeRobot, etc.</p><p>But pinging the home page has its limits. As you gain experience with that metric, you may decide to measure more high fidelity and organic metrics.</p><h3 class="header-anchor-post">Evaluation &amp; Investment<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§evaluation-and-investment" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/evaluation-and-investment" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h3><p>As a general rule of thumb: the closer to the top-left, the easier and cheaper it is to measure the SLI but the lower the quality it has.</p><p>The more you move to the bottom-right corner of the compass, the harder it is to measure and more costly it gets but the quality improves.</p><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!RYZ0!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!RYZ0!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png 424w, https://substackcdn.com/image/fetch/$s_!RYZ0!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png 848w, https://substackcdn.com/image/fetch/$s_!RYZ0!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png 1272w, https://substackcdn.com/image/fetch/$s_!RYZ0!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!RYZ0!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png" width="1061" height="1061" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1061,&quot;width&quot;:1061,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:1224962,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!RYZ0!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png 424w, https://substackcdn.com/image/fetch/$s_!RYZ0!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png 848w, https://substackcdn.com/image/fetch/$s_!RYZ0!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png 1272w, https://substackcdn.com/image/fetch/$s_!RYZ0!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><h3 class="header-anchor-post">Evolution<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§evolution" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/evolution" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h3><p>Over time, you may want to carefully move your measurement from the top-left to the bottom-right corner considering the ROI.</p><p>You may go from simple synthetic to complex synthetic or simple organic. Eventually you may end up with complex organic SLIs.</p><div class="captioned-image-container"><figure><a target="_blank" href="https://substackcdn.com/image/fetch/$s_!M765!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png" data-component-name="Image2ToDOM" class="image-link image2 is-viewable-img can-restack"><div class="image2-inset"><picture><source type="image/webp" srcset="https://substackcdn.com/image/fetch/$s_!M765!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 424w, https://substackcdn.com/image/fetch/$s_!M765!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 848w, https://substackcdn.com/image/fetch/$s_!M765!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!M765!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 1456w" sizes="100vw"/><img src="https://substackcdn.com/image/fetch/$s_!M765!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png" width="1061" height="1062" data-attrs="{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1062,&quot;width&quot;:1061,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:1167545,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}" alt srcset="https://substackcdn.com/image/fetch/$s_!M765!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 424w, https://substackcdn.com/image/fetch/$s_!M765!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 848w, https://substackcdn.com/image/fetch/$s_!M765!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!M765!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 1456w" sizes="100vw" loading="lazy" class="sizing-normal"/></picture><div class="image-link-expand"><div class="pencraft pc-display-flex pc-gap-8 pc-reset"><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container restack-image"><svg aria-hidden="true" width="20" height="20" viewBox="0 0 20 20" fill="none" stroke-width="1.5" stroke="var(--color-fg-primary)" stroke-linecap="round" stroke-linejoin="round" xmlns="http://www.w3.org/2000/svg"><g><path d="M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882"></path></g></svg></button><button tabindex="0" type="button" class="pencraft pc-reset pencraft icon-container view-image"><svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-maximize2 lucide-maximize-2"><polyline points="15 3 21 3 21 9"></polyline><polyline points="9 21 3 21 3 15"></polyline><line x1="21" x2="14" y1="3" y2="10"></line><line x1="3" x2="10" y1="21" y2="14"></line></svg></button></div></div></div></a></figure></div><p></p><p>Alternatively, maybe you’re in 4 but the SLI is too expensive for what it’s doing. Therefore you may deliberately go for a cheaper measurement with lower or equal quality.</p><h3 class="header-anchor-post">Final Thoughts<div class="pencraft pc-display-flex pc-alignItems-center pc-position-absolute pc-reset header-anchor-parent"><div class="pencraft pc-display-contents pc-reset pubTheme-yiXxQA"><div id="§final-thoughts" class="pencraft pc-reset header-anchor offset-top"></div><button tabindex="0" type="button" aria-label="Link" data-href="https://blog.alexewerlof.com/i/170275899/final-thoughts" class="pencraft pc-reset pencraft iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_secondary-S63h9o"><svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-link"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path></svg></button></div></div></h3><p><span>The quality of your SLI depends on the story it tells. It must reflect the consumer's experience. This is crucial. An SRE's </span><strong>error budget</strong><span> must always be tied to a metric that accurately reflects user’s tolerance for failure.</span></p><p>The SLI Compass provides a clear path for evaluation, investment and evolution. You can use it to design and refine your SLIs. SLIs are not a one-size-fits-all metric. Make a conscious choice with signal to noise ratio and ROI in mind to reduce alerting false positives or false negatives.</p><div data-attrs="{&quot;url&quot;:&quot;https://blog.alexewerlof.com/p/sli-compass?utm_source=substack&amp;utm_medium=email&amp;utm_content=share&amp;action=share&quot;,&quot;text&quot;:&quot;Share&quot;}" data-component-name="CaptionedButtonToDOM" class="captioned-button-wrap"><div class="preamble"><p class="cta-caption">If you found this post insightful, please share it on social media and your networks to inspire others</p></div><p data-attrs="{&quot;url&quot;:&quot;https://blog.alexewerlof.com/p/sli-compass?utm_source=substack&amp;utm_medium=email&amp;utm_content=share&amp;action=share&quot;,&quot;text&quot;:&quot;Share&quot;}" data-component-name="ButtonCreateButton" class="button-wrapper"><a href="https://blog.alexewerlof.com/p/sli-compass?utm_source=substack&amp;utm_medium=email&amp;utm_content=share&amp;action=share" class="button primary"><span>Share</span></a></p></div><div><hr/></div><p><em><a href="https://blog.alexewerlof.com/p/faq#%C2%A7payment">My monetization strategy</a><span> is to give away most content for free but hese posts take anywhere from a few hours to a few days to draft, edit, research, illustrate, and publish. 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Ewerlöf</button></div></div><div class="pencraft pc-display-flex pc-flexDirection-column pc-reset flex-grow-rzmknG"></div><div class="pencraft pc-display-flex pc-reset comment-menu-trigger-container triggerContainer-eX588u"><button tabindex="0" type="button" aria-label="Ellipsis" id="radix-P0-87" aria-haspopup="menu" aria-expanded="false" data-state="closed" class="pencraft pc-reset pencraft trigger-j08Uop iconButton-mq_Et5 iconButtonBase-dJGHgN buttonBase-GK1x3M buttonStyle-r7yGCK size_sm-G3LciD priority_quaternary-kpMibu"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-ellipsis"><circle cx="12" cy="12" r="1"></circle><circle cx="19" cy="12" r="1"></circle><circle cx="5" cy="12" r="1"></circle></svg></button></div></div><div class="comment-body expanded"><p><span>Hi, Alex. It seems like a high fidelity SLI is essentially an QA integration test. Is that accurate to say?</span></p></div><div class="pencraft pc-display-flex pc-gap-16 pc-paddingTop-8 pc-justifyContent-flex-start pc-alignItems-center pc-reset comment-actions withShareButton-hQzuEn"><span class="pencraft pc-reset decoration-hover-underline-ClDVRM reset-IxiVJZ"><a class="pencraft pc-reset link-_X6et2 link-LIBpto"><div class="pencraft pc-display-flex pc-gap-6 pc-alignItems-center pc-reset"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="var(--color-fg-secondary-themed)" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-message-circle"><path d="M7.9 20A9 9 0 1 0 4 16.1L2 22Z"></path></svg><div class="pencraft pc-reset color-pub-secondary-text-hGQ02T line-height-20-t4M0El font-meta-MWBumP size-11-NuY2Zx weight-medium-fw81nC transform-uppercase-yKDgcq reset-IxiVJZ meta-EgzBVA comment-actions-label">Reply</div></div></a></span><span class="pencraft pc-reset 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We discuss 2 dimension: fidelity shows how closely your SLI is measuring the user experience, granularity shows how many parameter are measured by your SLI.\\nLearn how to quickly evaluate existing SLIs and choose new ones based on their cost, complexity, and signal-to-noise ratio.\",\"search_engine_title\":null,\"section_id\":67723,\"should_send_free_preview\":true,\"show_guest_bios\":true,\"slug\":\"sli-compass\",\"social_title\":\"SLI Compass: Fidelity and Granulairty\",\"subtitle\":\"A Mental Model to Assess Existing SLIs and Evaluate New Ones\",\"teaser_post_eligible\":true,\"title\":\"SLI Compass: Fidelity and Granularity\",\"type\":\"newsletter\",\"video_upload_id\":null,\"write_comment_permissions\":\"everyone\",\"meter_type\":\"none\",\"live_stream_id\":null,\"is_published\":true,\"restacks\":2,\"reactions\":{\"\u2764\":11},\"top_exclusions\":[],\"pins\":[],\"section_pins\":[],\"has_shareable_clips\":false,\"previous_post_slug\":\"service-level-topology\",\"next_post_slug\":\"sli-evolution-stages\",\"cover_image\":\"https://substackcdn.com/image/fetch/$s_!5TKM!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png\",\"cover_image_is_square\":true,\"cover_image_is_explicit\":false,\"videoUpload\":null,\"podcastFields\":{\"post_id\":170275899,\"podcast_episode_number\":null,\"podcast_season_number\":null,\"podcast_episode_type\":null,\"should_syndicate_to_other_feed\":null,\"syndicate_to_section_id\":null,\"hide_from_feed\":false,\"free_podcast_url\":null,\"free_podcast_duration\":null,\"preview_contains_ad\":false,\"was_imported_self_serve_sync\":false,\"draft_free_podcast_url\":null,\"draft_free_podcast_duration\":null},\"podcastUpload\":null,\"podcastPreviewUpload\":null,\"voiceover_upload_id\":null,\"voiceoverUpload\":null,\"has_voiceover\":false,\"description\":\"A Mental Model to Assess Existing SLIs and Evaluate New Ones. We discuss 2 dimension: fidelity shows how closely your SLI is measuring the user experience, granularity shows how many parameter are measured by your SLI\",\"body_html\":\"<p><a href=\\\"https://blog.alexewerlof.com/p/sli\\\">Service Level Indicator</a> (SLIs) is a fundamental concept in reliability engineering. Done right, it quantifies the level of service from the consumer\u2019s point of view in line with the business objectives.</p><p>However, different SLIs have different signal to noise ratio and ROI (return on investment).</p><p>This article introduces SLI Compass, a 2D mental model to help you:</p><ul><li><p>Quickly assess the signal/noise ratio of existing SLIs</p></li><li><p>Evaluate SLIs based on their cost and complexity</p></li><li><p>Set a direction for improving the quality of existing SLIs at a reasonable ROI</p></li></ul><p>The goal is to help senior engineers, technical and engineering leaders to pick the right SLI based on product maturity, budget, timing, and usage patterns.</p><p class=\\\"button-wrapper\\\" data-attrs=\\\"{&quot;url&quot;:&quot;https://blog.alexewerlof.com/subscribe?&quot;,&quot;text&quot;:&quot;Subscribe now&quot;,&quot;action&quot;:null,&quot;class&quot;:null}\\\" data-component-name=\\\"ButtonCreateButton\\\"><a class=\\\"button primary\\\" href=\\\"https://blog.alexewerlof.com/subscribe?\\\"><span>Subscribe now</span></a></p><h1>Categorizing SLIs</h1><p>I\u2019ve gone through hundreds of architectures with tens of teams over the years both at my companies and external clients.</p><p>In my experience the most common SLIs are:</p><ul><li><p><strong>Availability:</strong> is the service available to the consumer and can it be used for their tasks? This is by far the most common SLI except for async services like queues where other metrics make more sense.</p></li><li><p><strong>Latency:</strong> how long does it take to interact with the service? This is very common for user-facing services, or services that have a time-critical consumption like Frontend, API, Databases, CDN, queued workload processing, etc.</p></li><li><p><strong>Success rate:</strong> how often do consumers manage to fulfill their task? This is common with transactional services like REST APIs, user journeys, or even queued workload (e.g. dead-letter queue).</p></li><li><p><strong>Efficiency:</strong> is the service operating with the right trade-offs that makes business sense? For example: are we using too much GPU for free user requests? Is the Cache being utilized? Are queued work being processed? etc.</p></li></ul><p>There are also other niche metrics like correctness, freshness, relevance, etc.</p><p>All SLIs can be mapped in a 2D axis:</p><ul><li><p><strong>Fidelity:</strong> how closely does the SLI represent the consumer experience?</p></li><li><p><strong>Granularity:</strong> how many variables and parameters are aggregated in a single data point?</p></li></ul><p>We can combine these two dimensions to get a powerful but familiar quadrant model.</p><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!5TKM!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!5TKM!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 424w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 848w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 1272w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 1456w\\\" sizes=\\\"100vw\\\"><img src=\\\"https://substackcdn.com/image/fetch/$s_!5TKM!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png\\\" width=\\\"1062\\\" height=\\\"1061\\\" data-attrs=\\\"{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1061,&quot;width&quot;:1062,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:1800473,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}\\\" class=\\\"sizing-normal\\\" alt=\\\"\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!5TKM!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 424w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 848w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 1272w, https://substackcdn.com/image/fetch/$s_!5TKM!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F0042de0b-3173-4670-b9ba-964757a0e1c0_1062x1061.png 1456w\\\" sizes=\\\"100vw\\\" loading=\\\"lazy\\\"></picture><div class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p>As we will see, a single category of SLIs like availability or latency, can fit into any of those 4 quadrants.</p><h1>The two dimensions</h1><h2>1. Fidelity: how closely does the SLI represent the consumer experience?</h2><p>SLI <strong>Fidelity</strong>, refers to how the data, or telemetry, is generated and how accurately it represents the consumer\u2019s experience of the service.</p><ul><li><p><strong>Synthetic metrics</strong> use artificial, fake, or simulated loads. A common example is a tool that pings an endpoint every minute to gather data about latency or availability. This check ensures the endpoint is responsive.</p></li><li><p><strong>Organic metrics</strong> gather data from consumers actually using the service. For example, we can gather availability and latency data from API gateway that exposes a service externally. This is a more precise way to measure service level.</p></li></ul><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!Y06S!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!Y06S!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 1456w\\\" sizes=\\\"100vw\\\"><img src=\\\"https://substackcdn.com/image/fetch/$s_!Y06S!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png\\\" width=\\\"1063\\\" height=\\\"1062\\\" 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srcset=\\\"https://substackcdn.com/image/fetch/$s_!Y06S!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!Y06S!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F383ec274-9944-4227-8403-36f127899717_1063x1062.png 1456w\\\" sizes=\\\"100vw\\\" loading=\\\"lazy\\\"></picture><div class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p>Organic metrics are more realistic. They map directly to what's happening in production.</p><p>However, they can be harder to measure. For high-traffic services, they can generate massive amounts of data. This requires a more robust and costly monitoring infrastructure.</p><p>For low-traffic services, there may not be enough organic load to for the SLI formula to work correctly. That\u2019s because SLI status (also known as <a href=\\\"https://blog.alexewerlof.com/p/sls\\\">SLS</a>), is a percentage based.</p><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!Hf1l!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!Hf1l!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 424w, 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data-attrs=\\\"{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:601,&quot;width&quot;:1060,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:67719,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}\\\" class=\\\"sizing-normal\\\" alt=\\\"\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!Hf1l!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 424w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 848w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 1272w, https://substackcdn.com/image/fetch/$s_!Hf1l!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F43c8b208-e775-4d48-bbd6-831f61978957_1060x601.png 1456w\\\" sizes=\\\"100vw\\\" loading=\\\"lazy\\\"></picture><div class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p>For example, if a service receives 50 request per months, it is not reasonable to expect a success rate of 99% because a single failure in that period reduces the service level status (SLS) to 98%. In this case, one solution can be to use synthetic metric.</p><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!aIfH!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!aIfH!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 424w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 848w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 1272w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 1456w\\\" sizes=\\\"100vw\\\"><img src=\\\"https://substackcdn.com/image/fetch/$s_!aIfH!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png\\\" width=\\\"1060\\\" height=\\\"695\\\" data-attrs=\\\"{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/ac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:695,&quot;width&quot;:1060,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:58981,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}\\\" class=\\\"sizing-normal\\\" alt=\\\"\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!aIfH!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 424w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 848w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 1272w, https://substackcdn.com/image/fetch/$s_!aIfH!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fac448d34-032c-4ea4-9d39-dc5d80a8d893_1060x695.png 1456w\\\" sizes=\\\"100vw\\\" loading=\\\"lazy\\\"></picture><div class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p>Synthetic load can potentially skew product metrics. For example, if the product is measuring MAU (monthly active users), it\u2019s important to have a way to distinguish fake users (synthetic) from the real ones. Otherwise, wrong data can lead to wrong decisions.</p><h2>2. Granularity: How many variables are aggregated by the SLI data points?</h2><p>Let's look at the second dimension of SLIs: their <strong>granularity</strong>, which refers to the number of parameters or variables being tested to quantify the level of the service.</p><ul><li><p><strong>Simple: </strong>measure only one thing. For example, a simple metric might check if an endpoint returns a <code>200</code> HTTP status code (for availability) or if a single API call's latency is below a threshold. This tells you the basic health of one component. It acts as a basic <strong>proxy</strong> for overall service health. It doesn't say if the service is actually useful to the consumer's complete task.</p></li><li><p><strong>Complex:</strong> measure multipel things. This tells a richer story about the <strong>consumer journey</strong> or complex system behavior. A high-fidelity metric could track the success rate and latency of all steps in a critical user purchase flow. It ensures they are working as expected.</p></li></ul><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!lnLL!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!lnLL!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 1456w\\\" sizes=\\\"100vw\\\"><img src=\\\"https://substackcdn.com/image/fetch/$s_!lnLL!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png\\\" width=\\\"1063\\\" height=\\\"1062\\\" data-attrs=\\\"{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1062,&quot;width&quot;:1063,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:435243,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}\\\" class=\\\"sizing-normal\\\" alt=\\\"\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!lnLL!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!lnLL!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F435c4dfe-70d7-44fb-beb8-44ff3cbe40d5_1063x1062.png 1456w\\\" sizes=\\\"100vw\\\" loading=\\\"lazy\\\"></picture><div class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p>Complex SLIs aggregate multiple variables. For example, instead of pinging the home page (simple), we run a <a href=\\\"https://playwright.dev/\\\">Playwright</a> script that traverses a user journey to identify any broken step.</p><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!bkoT!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!bkoT!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 424w, 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data-attrs=\\\"{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:565,&quot;width&quot;:1059,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:53520,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}\\\" class=\\\"sizing-normal\\\" alt=\\\"\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!bkoT!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 424w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 848w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 1272w, https://substackcdn.com/image/fetch/$s_!bkoT!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F9b56f234-3454-470f-9092-1f545fd2cfee_1059x565.png 1456w\\\" sizes=\\\"100vw\\\" loading=\\\"lazy\\\"></picture><div class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p>Complex SLIs can be more costly to maintain.</p><p>They might also introduce a lag in flagging an incident because they have to wait to get data for all variables. This is because they require more data processing and aggregation.</p><p>However, complex SLIs provide a higher-quality signal because they reflect a user's experience more accurately.</p><p>On the flipside, it can be harder to reason about the complex SLIs due to aggregation: if there\u2019s a failure, what did exactly fail?</p><p>To answer that question, we need to store more data, which adds to the cost of complex SLIs.</p><p>One caveat for complex SLIs is the ownership of different variables. Most metrics aggregate multiple variables.</p><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!mbrn!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!mbrn!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 424w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 848w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 1272w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 1456w\\\" sizes=\\\"100vw\\\"><img src=\\\"https://substackcdn.com/image/fetch/$s_!mbrn!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png\\\" width=\\\"1035\\\" height=\\\"912\\\" data-attrs=\\\"{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:912,&quot;width&quot;:1035,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:77498,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}\\\" class=\\\"sizing-normal\\\" alt=\\\"\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!mbrn!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 424w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 848w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 1272w, https://substackcdn.com/image/fetch/$s_!mbrn!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F6c7f2097-1de5-46da-b4b6-1d55b32c5e9e_1035x912.png 1456w\\\" sizes=\\\"100vw\\\" loading=\\\"lazy\\\"></picture><div class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p>Ideally you want each data point to only aggregate variables that are within the control of one team. Because when the metric shows a service degradation or disruption, it is easy to reason about who owns the service and should receive an alert to fix it.</p><h2>Putting it together</h2><p>Putting everything together, we get this 2D Compass:</p><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!v_yw!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!v_yw!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 1456w\\\" sizes=\\\"100vw\\\"><img src=\\\"https://substackcdn.com/image/fetch/$s_!v_yw!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png\\\" width=\\\"1063\\\" height=\\\"1062\\\" data-attrs=\\\"{&quot;src&quot;:&quot;https://substack-post-media.s3.amazonaws.com/public/images/239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png&quot;,&quot;srcNoWatermark&quot;:null,&quot;fullscreen&quot;:null,&quot;imageSize&quot;:null,&quot;height&quot;:1062,&quot;width&quot;:1063,&quot;resizeWidth&quot;:null,&quot;bytes&quot;:474836,&quot;alt&quot;:null,&quot;title&quot;:null,&quot;type&quot;:&quot;image/png&quot;,&quot;href&quot;:null,&quot;belowTheFold&quot;:true,&quot;topImage&quot;:false,&quot;internalRedirect&quot;:&quot;https://blog.alexewerlof.com/i/170275899?img=https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png&quot;,&quot;isProcessing&quot;:false,&quot;align&quot;:null,&quot;offset&quot;:false}\\\" class=\\\"sizing-normal\\\" alt=\\\"\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!v_yw!,w_424,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 424w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_848,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 848w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_1272,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!v_yw!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F239dc36d-8ee5-46ae-b86a-6e36c6d35a8a_1063x1062.png 1456w\\\" sizes=\\\"100vw\\\" loading=\\\"lazy\\\"></picture><div class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><h1>Examples</h1><p>Availability is the most common SLIs. At the basic level it\u2019s an answer to this question:</p><blockquote><p>Is the service exposed to the consumer?</p></blockquote><p>However, a better question can be:</p><blockquote><p>Can the consumer use the service to do their tasks and achieve their goals?</p></blockquote><p>The difference is subtle but important:</p><ul><li><p>The former is aligned with the <strong>service provider</strong>\u2019s basic commitment and is usually easier to measure.</p></li><li><p>The latter is aligned with the <strong>service consumer</strong>\u2019s expectation and is typically harder to measure.</p></li></ul><div class=\\\"digest-post-embed\\\" data-attrs=\\\"{&quot;nodeId&quot;:&quot;73c6460d-1ea9-47ae-a724-49c467ad6fbf&quot;,&quot;caption&quot;:&quot;In the context of service levels, there are multiple terms that are related to each other. This post serves as a glossary to define and connect:&quot;,&quot;cta&quot;:&quot;Read full story&quot;,&quot;showBylines&quot;:true,&quot;showDescription&quot;:true,&quot;showImage&quot;:true,&quot;size&quot;:&quot;sm&quot;,&quot;isEditorNode&quot;:true,&quot;title&quot;:&quot;Service Level Terminology&quot;,&quot;publishedBylines&quot;:[{&quot;id&quot;:87732486,&quot;name&quot;:&quot;Alex Ewerl\u00F6f&quot;,&quot;bio&quot;:&quot;Writes about technical leadership, growth mindset, and system reliability engineering.\\\\n\\\\nSenior Staff Engineer, MSc Systems Engineering from KTH, Stockholmer, dad, amateur artist.\\\\n\\\\nRead more here: https://www.alexewerlof.com/who&quot;,&quot;photo_url&quot;:&quot;https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fbucketeer-e05bbc84-baa3-437e-9518-adb32be77984.s3.amazonaws.com%2Fpublic%2Fimages%2Fe2713990-da82-481b-b579-01a7aaa5b85b_560x560.jpeg&quot;,&quot;is_guest&quot;:false,&quot;bestseller_tier&quot;:null}],&quot;post_date&quot;:&quot;2024-10-25T03:16:15.538Z&quot;,&quot;cover_image&quot;:&quot;https://substackcdn.com/image/fetch/$s_!MlI7!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F5bb74595-f0d9-4d19-9a4c-23d596b721a8_1010x1122.png&quot;,&quot;cover_image_alt&quot;:null,&quot;canonical_url&quot;:&quot;https://blog.alexewerlof.com/p/service-level-terminology&quot;,&quot;section_name&quot;:&quot;Reliability Engineering&quot;,&quot;video_upload_id&quot;:null,&quot;id&quot;:150614488,&quot;type&quot;:&quot;newsletter&quot;,&quot;reaction_count&quot;:19,&quot;comment_count&quot;:4,&quot;publication_id&quot;:null,&quot;publication_name&quot;:&quot;Alex Ewerl\u00F6f Notes&quot;,&quot;publication_logo_url&quot;:&quot;https://substackcdn.com/image/fetch/$s_!_Ur2!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8c58cb07-9341-402b-bcdb-9fa767c2cdac_500x500.png&quot;,&quot;belowTheFold&quot;:true,&quot;youtube_url&quot;:null,&quot;show_links&quot;:null,&quot;feed_url&quot;:null}\\\"></div><p>How can we measure availability for an API server?</p><ol><li><p><strong>Simple &amp; Synthetic:</strong> ping the health endpoint every minute and calculate the percentage of successful pings in a <a href=\\\"https://blog.alexewerlof.com/p/compliance-period\\\">period</a></p></li><li><p><strong>Simple &amp; Organic:</strong> count the number of minutes where the API endpoint could handle valid requests (i.e. with valid auth header) in a <a href=\\\"https://blog.alexewerlof.com/p/compliance-period\\\">period</a></p></li><li><p><strong>Complex &amp; Synthetic:</strong> use synthetic monitoring to test that the critical user flow (e.g. a purchase journey) works and calculate the successful execution percentage</p></li><li><p><strong>Complex &amp; Organic:</strong> use the RUM (real-user monitoring) data to identify any broken user journeys and calculate successful user sessions</p></li></ol><p>Let\u2019s do this exercise for latency, which is the second most common SLI:</p><ol><li><p><strong>Simple &amp; Synthetic:</strong> Measure the response time of a periodic <code>GET</code> request to a predesignated endpoint (i.e. <code>www.example.com/api/health</code>) and calculate the <a href=\\\"https://blog.alexewerlof.com/p/percentile\\\">P99 percentile</a> over a <a href=\\\"https://blog.alexewerlof.com/p/compliance-period\\\">period</a>.</p></li><li><p><strong>Simple &amp; Organic:</strong> Calculate the <a href=\\\"https://blog.alexewerlof.com/p/percentile\\\">P99 percentile</a> latency for all successful API requests from real users as measured at the API gateway.</p></li><li><p><strong>Complex &amp; Synthetic:</strong> periodically simulate a complete user transaction (e.g., login, search, add to cart, checkout) and measure the end-to-end response time.</p></li><li><p><strong>Complex &amp; Organic:</strong> Analyze Real User Monitoring (RUM) data to track the full-page load time, including all resource fetches and rendering, for critical user journeys.</p></li></ol><h1>Signal to noise ratio</h1><p>Good SLIs are worthy of being on-call for because they indicate service <a href=\\\"https://blog.alexewerlof.com/p/service-degradation-vs-disruption\\\">degradation or disruption</a> with high accuracy. Even if there is no 24/7 on-call rotation, this is still a good mindset to evaluate an SLI:</p><ol><li><p><strong>Does this SLI help us get notified when there is an incident?</strong><br>(incident in this context is any failure that threatens the business objective)</p></li><li><p><strong>Does each anomaly in this SLI indicate an incident?</strong><br>(no false positive or false negative)</p></li></ol><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!bkSH!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!bkSH!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 424w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 848w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 1272w, https://substackcdn.com/image/fetch/$s_!bkSH!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png 1456w\\\" sizes=\\\"100vw\\\"><img src=\\\"https://substackcdn.com/image/fetch/$s_!bkSH!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8860290e-8185-4cd2-abf5-c63dc25b824d_1038x992.png\\\" width=\\\"1038\\\" height=\\\"992\\\" 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class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p>SLI is the basis for a solid ownership implementation:</p><ul><li><p>SLI measures the level of service from consumer\u2019s perspective</p></li><li><p><a href=\\\"https://blog.alexewerlof.com/p/slo\\\">SLO</a> helps:</p><ul><li><p>The stakeholders set expectations on the service owner</p></li><li><p>The service owner communicate their commitment to service consumers</p></li></ul></li><li><p>Alerts: tie that expectation or commitment to responsibility and accountability</p></li></ul><p>Poor SLIs lead to broken ownership.</p><div class=\\\"digest-post-embed\\\" data-attrs=\\\"{&quot;nodeId&quot;:&quot;71178ecb-e30a-463a-90f0-30640769e5ef&quot;,&quot;caption&quot;:&quot;Have you been in any of these situations?&quot;,&quot;cta&quot;:&quot;Read full story&quot;,&quot;showBylines&quot;:true,&quot;showDescription&quot;:true,&quot;showImage&quot;:true,&quot;size&quot;:&quot;sm&quot;,&quot;isEditorNode&quot;:true,&quot;title&quot;:&quot;6 Archetypes of Broken Ownership&quot;,&quot;publishedBylines&quot;:[{&quot;id&quot;:87732486,&quot;name&quot;:&quot;Alex Ewerl\u00F6f&quot;,&quot;bio&quot;:&quot;Writes about technical leadership, growth mindset, and system reliability engineering.\\\\n\\\\nSenior Staff Engineer, MSc Systems Engineering from KTH, Stockholmer, dad, amateur artist.\\\\n\\\\nRead more here: https://www.alexewerlof.com/who&quot;,&quot;photo_url&quot;:&quot;https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fbucketeer-e05bbc84-baa3-437e-9518-adb32be77984.s3.amazonaws.com%2Fpublic%2Fimages%2Fe2713990-da82-481b-b579-01a7aaa5b85b_560x560.jpeg&quot;,&quot;is_guest&quot;:false,&quot;bestseller_tier&quot;:null}],&quot;post_date&quot;:&quot;2023-08-01T17:10:54.401Z&quot;,&quot;cover_image&quot;:&quot;https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F72091ddc-6191-4ccb-8d06-15a7edbed199_1012x964.png&quot;,&quot;cover_image_alt&quot;:null,&quot;canonical_url&quot;:&quot;https://blog.alexewerlof.com/p/broken-ownership&quot;,&quot;section_name&quot;:&quot;Reliability Engineering&quot;,&quot;video_upload_id&quot;:null,&quot;id&quot;:135623153,&quot;type&quot;:&quot;newsletter&quot;,&quot;reaction_count&quot;:65,&quot;comment_count&quot;:7,&quot;publication_id&quot;:null,&quot;publication_name&quot;:&quot;Alex Ewerl\u00F6f Notes&quot;,&quot;publication_logo_url&quot;:&quot;https://substackcdn.com/image/fetch/$s_!_Ur2!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F8c58cb07-9341-402b-bcdb-9fa767c2cdac_500x500.png&quot;,&quot;belowTheFold&quot;:true,&quot;youtube_url&quot;:null,&quot;show_links&quot;:null,&quot;feed_url&quot;:null}\\\"></div><h1>Pro Tips: When and how to use the SLI compass?</h1><p>Broadly speaking there are 3 categories of use cases for SLI compass:</p><ol><li><p><strong>Evaluation:</strong> Assess the signal quality of an SLI and its effectiveness in implementing <a href=\\\"https://blog.alexewerlof.com/p/you-build-it-you-own-it\\\">full ownership</a> through alerts.</p></li><li><p><strong>Investment:</strong> Estimate the <a href=\\\"https://blog.alexewerlof.com/p/tech-bet\\\">ROI (return on investment)</a> of an existing or new SLI</p></li><li><p><strong>Evolution:</strong> motivate improving how tech health is measured using <a href=\\\"https://blog.alexewerlof.com/p/sli\\\">SLI</a> and <a href=\\\"https://blog.alexewerlof.com/p/premature-optimization\\\">optimized</a> towards an <a href=\\\"https://blog.alexewerlof.com/p/slo\\\">SLO</a></p></li></ol><p>For example, when Service Levels (as a concept) is new to an organization, you want to start small and easy. A simple synthetic check like pinging the home page every minute is a pretty good start.</p><p>In fact, this is so common that there\u2019s a whole product sector doing exactly that: Pingdom, UptimeRobot, etc.</p><p>But pinging the home page has its limits. As you gain experience with that metric, you may decide to measure more high fidelity and organic metrics.</p><h3>Evaluation &amp; Investment</h3><p>As a general rule of thumb: the closer to the top-left, the easier and cheaper it is to measure the SLI but the lower the quality it has.</p><p>The more you move to the bottom-right corner of the compass, the harder it is to measure and more costly it gets but the quality improves.</p><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!RYZ0!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4d18c7ea-7f14-4cf2-b302-1c76d52b104f_1061x1061.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" 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view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><h3>Evolution</h3><p>Over time, you may want to carefully move your measurement from the top-left to the bottom-right corner considering the ROI.</p><p>You may go from simple synthetic to complex synthetic or simple organic. Eventually you may end up with complex organic SLIs.</p><div class=\\\"captioned-image-container\\\"><figure><a class=\\\"image-link image2 is-viewable-img\\\" target=\\\"_blank\\\" href=\\\"https://substackcdn.com/image/fetch/$s_!M765!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png\\\" data-component-name=\\\"Image2ToDOM\\\"><div class=\\\"image2-inset\\\"><picture><source type=\\\"image/webp\\\" srcset=\\\"https://substackcdn.com/image/fetch/$s_!M765!,w_424,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 424w, https://substackcdn.com/image/fetch/$s_!M765!,w_848,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 848w, https://substackcdn.com/image/fetch/$s_!M765!,w_1272,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 1272w, https://substackcdn.com/image/fetch/$s_!M765!,w_1456,c_limit,f_webp,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png 1456w\\\" sizes=\\\"100vw\\\"><img src=\\\"https://substackcdn.com/image/fetch/$s_!M765!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4a8eea6e-be1b-47a1-a0c1-2a647acdea89_1061x1062.png\\\" width=\\\"1061\\\" height=\\\"1062\\\" 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class=\\\"image-link-expand\\\"><div class=\\\"pencraft pc-display-flex pc-gap-8 pc-reset\\\"><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container restack-image\\\"><svg aria-hidden=\\\"true\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 20 20\\\" fill=\\\"none\\\" stroke-width=\\\"1.5\\\" stroke=\\\"var(--color-fg-primary)\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" xmlns=\\\"http://www.w3.org/2000/svg\\\"><g><path d=\\\"M2.53001 7.81595C3.49179 4.73911 6.43281 2.5 9.91173 2.5C13.1684 2.5 15.9537 4.46214 17.0852 7.23684L17.6179 8.67647M17.6179 8.67647L18.5002 4.26471M17.6179 8.67647L13.6473 6.91176M17.4995 12.1841C16.5378 15.2609 13.5967 17.5 10.1178 17.5C6.86118 17.5 4.07589 15.5379 2.94432 12.7632L2.41165 11.3235M2.41165 11.3235L1.5293 15.7353M2.41165 11.3235L6.38224 13.0882\\\"></path></g></svg></button><button tabindex=\\\"0\\\" type=\\\"button\\\" class=\\\"pencraft pc-reset pencraft icon-container view-image\\\"><svg xmlns=\\\"http://www.w3.org/2000/svg\\\" width=\\\"20\\\" height=\\\"20\\\" viewBox=\\\"0 0 24 24\\\" fill=\\\"none\\\" stroke=\\\"currentColor\\\" stroke-width=\\\"2\\\" stroke-linecap=\\\"round\\\" stroke-linejoin=\\\"round\\\" class=\\\"lucide lucide-maximize2 lucide-maximize-2\\\"><polyline points=\\\"15 3 21 3 21 9\\\"></polyline><polyline points=\\\"9 21 3 21 3 15\\\"></polyline><line x1=\\\"21\\\" x2=\\\"14\\\" y1=\\\"3\\\" y2=\\\"10\\\"></line><line x1=\\\"3\\\" x2=\\\"10\\\" y1=\\\"21\\\" y2=\\\"14\\\"></line></svg></button></div></div></div></a></figure></div><p></p><p>Alternatively, maybe you\u2019re in 4 but the SLI is too expensive for what it\u2019s doing. Therefore you may deliberately go for a cheaper measurement with lower or equal quality.</p><h3>Final Thoughts</h3><p>The quality of your SLI depends on the story it tells. It must reflect the consumer's experience. This is crucial. An SRE's <strong>error budget</strong> must always be tied to a metric that accurately reflects user\u2019s tolerance for failure.</p><p>The SLI Compass provides a clear path for evaluation, investment and evolution. You can use it to design and refine your SLIs. SLIs are not a one-size-fits-all metric. Make a conscious choice with signal to noise ratio and ROI in mind to reduce alerting false positives or false negatives.</p><div class=\\\"captioned-button-wrap\\\" data-attrs=\\\"{&quot;url&quot;:&quot;https://blog.alexewerlof.com/p/sli-compass?utm_source=substack&utm_medium=email&utm_content=share&action=share&quot;,&quot;text&quot;:&quot;Share&quot;}\\\" data-component-name=\\\"CaptionedButtonToDOM\\\"><div class=\\\"preamble\\\"><p class=\\\"cta-caption\\\">If you found this post insightful, please share it on social media and your networks to inspire others</p></div><p class=\\\"button-wrapper\\\" data-attrs=\\\"{&quot;url&quot;:&quot;https://blog.alexewerlof.com/p/sli-compass?utm_source=substack&utm_medium=email&utm_content=share&action=share&quot;,&quot;text&quot;:&quot;Share&quot;}\\\" data-component-name=\\\"ButtonCreateButton\\\"><a class=\\\"button primary\\\" href=\\\"https://blog.alexewerlof.com/p/sli-compass?utm_source=substack&utm_medium=email&utm_content=share&action=share\\\"><span>Share</span></a></p></div><div><hr></div><p><em><a href=\\\"https://blog.alexewerlof.com/p/faq#%C2%A7payment\\\">My monetization strategy</a> is to give away most content for free but hese posts take anywhere from a few hours to a few days to draft, edit, research, illustrate, and publish. I pull these hours from my private time, vacation days and weekends. The simplest way to support this work is to <strong>like</strong>, <strong>subscribe</strong> and <strong>share</strong> it. If you really want to support me lifting our community, you can consider a paid subscription. If you want to save, you can get 20% off via <a href=\\\"https://blog.alexewerlof.com/protipsdiscount\\\">this link</a>. As a token of appreciation, subscribers get full access to the Pro-Tips sections and my online book <a href=\\\"https://blog.alexewerlof.com/p/rem\\\">Reliability Engineering Mindset</a>. Your contribution also funds my open-source products like <a href=\\\"https://slc.alexewerlof.com/\\\">Service Level Calculator</a>. You can also <a href=\\\"https://blog.alexewerlof.com/leaderboard\\\">invite your friends</a> to gain free access.</em></p><p><em>And to those of you who support me already, <strong>thank you</strong> for sponsoring this content for the others. \uD83D\uDE4C If you have questions or feedback, or you want me to dig deeper into something, please let me know in the comments.</em></p>\",\"has_dynamic_content\":false,\"truncated_body_text\":\"Service Level Indicator (SLIs) is a fundamental concept in reliability engineering. 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Senior Staff Engineer, MSc Systems Engineering from KTH, Stockholmer, dad, amateur artist. 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It seems like a high fidelity SLI is essentially an QA integration test. Is that accurate to say?\",\"body_json\":{\"type\":\"doc\",\"attrs\":{\"schemaVersion\":\"v1\"},\"content\":[{\"type\":\"paragraph\",\"content\":[{\"type\":\"text\",\"text\":\"Hi, Alex. It seems like a high fidelity SLI is essentially an QA integration test. 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