When a load test report says “p95 response time is above target”, the real question begins: is the delay in application code, the database, an external service or the infrastructure?
Teams that only look at the end-to-end time measured by the load tool answer that question with guesses. With APM and distributed tracing switched on during the test, you can see which service and which query every slow request passed through.
That is why we design performance work together with monitoring. The load scenario, the measurement points and the success criteria are part of the same plan. The result is a report that says “this query, at this load, waits this long” rather than “the system is slow”.
The same monitoring keeps running in production once testing ends. Performance testing stops being a one-off check and becomes comparable with real production behavior.