How do you troubleshoot a JMeter test producing artificially low response times due to caching?

Check whether an HTTP Cache Manager is present in the test plan and, if so, confirm its configuration - a Cache Manager honoring the target server's Expires/Cache-Control headers can cause JMeter to simulate a client-side cache hit and skip re-requesting a resource entirely, which shows up as an unrealistically fast (or entirely absent) sample for that request on later iterations.

Separately, check whether the target system itself has server-side or CDN-level caching returning a cached response for repeated identical requests - unlike client-side caching, this is a real server behavior, not a JMeter artifact, but it's worth distinguishing during analysis, since "fast because cached at the CDN" and "fast because JMeter simulated a client-side cache hit" point to two very different explanations and different next steps.

If the goal is to measure genuine server processing time uncontaminated by any caching layer, consider whether the Cache Manager should be disabled for this specific test, or whether cache-busting query parameters should be added to requests to force fresh responses - both are valid choices depending on whether you actually want to measure cached or uncached performance for this particular test's purpose.

Cross-check suspiciously fast samples against the actual response codes and sizes recorded for them - a client-side cache hit sometimes shows a distinctly different response code (like 304 Not Modified) or a notably smaller response size than a genuine full response, which is a useful diagnostic signal for confirming caching is actually what's happening rather than guessing based on timing alone.