Why Testing Your API Rate Limits Prevents Production Meltdowns
from Software Testing with Fexingo: QA, Automation, and Reliable Software Engineering Hosted by Fexingo
In episode 79 of Software Testing with Fexingo, Lucas and Luna dive into a topic that trips up even mature engineering teams: testing API rate limits before they break in production. They walk through a real example from a fintech startup that hit a 429 avalanche during a Black Friday sale in 2025, costing them $2 million in lost transactions and three days of firefighting. Lucas explains the difference between basic load testing and proper rate-limit boundary testing, why most teams test happy-path limits but ignore the reset-header behavior, and how a simple script that validates Retry-After headers and burst windows can reveal catastrophic bugs. Luna pushes back on the common assumption that rate-limit testing is just 'more load testing' and asks the practical question: how do you convince your team to prioritize this when the API hasn't failed yet? The conversation covers concrete techniques like token bucket vs. leaky bucket implementations, testing sliding window counters, and the gotchas of distributed rate limiting with Redis clusters. By the end, listeners will know exactly what to test in their next sprint and how to frame it to their lead engineer without sounding alarmist. #APIRateLimiting #429Errors #BoundaryTesting #PerformanceTesting #DistributedSystems #ReliabilityEngineering #Fintech #BlackFriday #LoadTesting #ChaosEngineering #SoftwareTesting #QA #Tech #FexingoBusiness #BusinessPodcast #SoftwareEngineering #APITesting #ResilienceTesting Keep every episode free: buymeacoffee.com/fexingo
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