Why Developers Should Use Percentiles, Not Averages, for System Monitoring

A SaaS engineering team configured API alerts based on average response times, which masked a serious performance problem affecting 5% of users experiencing delays over 2 seconds. Because the mean was pulled up by outliers rather than reflecting typical behavior, the alert fired constantly on false positives, training engineers to ignore it. A genuine outage then went undetected for 20 minutes as a result. Switching to 95th-percentile (p95) monitoring eliminated the false alarms and made tail latency visible. The incident illustrates a broader statistical principle: the summary metric chosen — mean, median, or percentile — fundamentally shapes what patterns engineers can and cannot see in their data.
This is an AI-generated summary. ShortSingh links to the original source for the complete article.


Discussion (0)
Log in to join the discussion and vote.
Log in