P50, P90, P95, and P99 are more valuable than averages.

P50, P90, P95, and P99 are more valuable than averages.

Many teams monitor average latency and think their application is healthy.

But averages hide what your users actually experience. Understanding percentiles helps you:

1. Measure real user experience
2. Set meaningful SLOs
3. Detect tail latency before customers complain
4. Know when not to use percentiles

These two visuals summarize the concepts I’ve found most useful for AWS

Explained P50, P90, P95, P99 in AWS

When not to use Percentiles

CloudWatch and application observability. Which metric do you monitor the most — Average, P95, or P99?