--- title: Load Testing for Traffic Spikes: When 200,000 Users... description: Scheduled traffic spikes from events like ticket presales, sports finals, and product launches keep breaking systems that pass ordinary load tests, because the... canonical: https://daily.dev/posts/load-testing-for-traffic-spikes-when-200-000-users-arrive-in-the-same-minute-dkd9non89 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Load Testing for Traffic Spikes: When 200,000 Users Arrive in the Same Minute | daily.dev og:description: Scheduled traffic spikes from events like ticket presales, sports finals, and product launches keep breaking systems that pass ordinary load tests, because the... og:url: https://daily.dev/posts/load-testing-for-traffic-spikes-when-200-000-users-arrive-in-the-same-minute-dkd9non89 og:image: https://api.daily.dev/og/posts/DKd9non89.png og:image:alt: Load Testing for Traffic Spikes: When 200,000 Users Arrive in the Same Minute og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Load Testing for Traffic Spikes: When 200,000 Users Arrive in the Same Minute **[Software Testing Magazine](https://daily.dev/sources/softwaretestingmagazine)** · 4 min read · 0 upvotes · 0 comments ## Summary Scheduled traffic spikes from events like ticket presales, sports finals, and product launches keep breaking systems that pass ordinary load tests, because the danger isn't total volume but ramp speed. Ticketmaster's 2022 Eras Tour presale hit 3.5 billion requests in a day, four times its prior peak, and buckled within an hour. Standard load tests miss what matters: how fast autoscalers lag behind vertical ramps, cold caches after deploys, and queues that never drain once retries start piling up. Slack's January 2021 outage illustrates the trap directly - packet loss on an AWS transit gateway lowered CPU usage, and the autoscaler misread that as calm and removed capacity during the year's busiest morning. Guidance for a truthful spike test: compress the ramp to under two minutes, test recovery after the peak fades, model bot traffic, use production-scale data, and measure error rates per endpoint rather than in aggregate. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why did Slack's autoscaler remove capacity during its busiest traffic morning in January 2021? An AWS transit gateway started dropping packets around 6 AM Pacific on January 4, 2021, causing servers to wait on the network and their CPU usage to drop. Slack's web tier scaled based on CPU usage, so the autoscaler interpreted the low CPU readings as calm conditions and removed capacity during the busiest morning of the year, worsening the outage. _Engineers debugging autoscaling metric blind spots can find similar incident breakdowns on daily.dev._ ### How many requests did Ticketmaster's Eras Tour presale generate and why did the site fail? The Eras Tour presale generated 3.5 billion system requests in a single day, about four times Ticketmaster's previous peak. The site buckled within an hour because the ramp to that volume happened almost instantly rather than gradually, and roughly 14 million entities (bots included) hit a presale meant for about 1.5 million invited fans. _Teams planning capacity for a launch can compare real-world spike incidents like this one on daily.dev._ ### What should a spike test do differently from a standard load test? A spike test should compress the ramp to full expected load in under two minutes instead of holding a fixed user count for an hour, test the recovery period after traffic falls (not just the peak), model bot and scraper traffic, run against production-scale data rather than a near-empty database, and measure error rates per endpoint since an aggregate 2 percent failure rate can hide a checkout flow failing 60 percent of the time. _Anyone building a spike-test plan for an upcoming launch can track load-testing techniques on daily.dev._ ## Similar posts on daily.dev - [Peak traffic prep: code slush, alert fatigue, crash cost](https://daily.dev/posts/peak-traffic-prep-code-slush-alert-fatigue-crash-cost-fljrbrl17) · Sentry Engineering · 0 upvotes · 0 comments - [Queueing Requests Queues Your Capacity Problems, Too](https://daily.dev/posts/queueing-requests-queues-your-capacity-problems-too-14qp4hjbt) · Programming Digest · 4 upvotes · 0 comments - [How Amazon Prepares for Black Friday](https://daily.dev/posts/how-amazon-prepares-for-black-friday-snyeugzq0) · The New Stack · 1 upvotes · 0 comments --- Tags: [#career](https://daily.dev/tags/career), [#load-testing](https://daily.dev/tags/load-testing) [View this post on daily.dev](https://daily.dev/posts/load-testing-for-traffic-spikes-when-200-000-users-arrive-in-the-same-minute-dkd9non89) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Load Testing for Traffic Spikes: When 200,000 Users Arrive in the Same Minute","url":"https://daily.dev/posts/load-testing-for-traffic-spikes-when-200-000-users-arrive-in-the-same-minute-dkd9non89","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/load-testing-for-traffic-spikes-when-200-000-users-arrive-in-the-same-minute-dkd9non89"},"datePublished":"2026-08-18T13:57:03.590Z","dateModified":"2026-08-18T14:05:45.561Z","description":"Scheduled traffic spikes from events like ticket presales, sports finals, and product launches keep breaking systems that pass ordinary load tests, because the...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/564541cf00582d19830c463b90d3d138?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/564541cf00582d19830c463b90d3d138?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Software Testing Magazine","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Software Testing Magazine","logo":"https://media.daily.dev/image/upload/s--51CB3vDJ--/f_auto/v1721572881/logos/softwaretestingmagazine","url":"https://daily.dev/sources/softwaretestingmagazine"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/load-testing-for-traffic-spikes-when-200-000-users-arrive-in-the-same-minute-dkd9non89","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"career,load-testing","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Software Testing Magazine","item":"https://daily.dev/sources/softwaretestingmagazine"},{"@type":"ListItem","position":3,"name":"Load Testing for Traffic Spikes: When 200,000 Users Arrive in the Same Minute"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/load-testing-for-traffic-spikes-when-200-000-users-arrive-in-the-same-minute-dkd9non89#faq","mainEntity":[{"@type":"Question","name":"Why did Slack's autoscaler remove capacity during its busiest traffic morning in January 2021?","acceptedAnswer":{"@type":"Answer","text":"An AWS transit gateway started dropping packets around 6 AM Pacific on January 4, 2021, causing servers to wait on the network and their CPU usage to drop. 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