How do execution and evidence connect?

Goal & mental model verified

HotSpot starts with interpretation and adaptively compiles hot code. Garbage collection manages object memory. Flight Recorder captures runtime events for diagnosis; request latency can include CPU, allocation, locks and external waiting.

Worked example · design exercise synthesis

A quote endpoint’s latency rises while CPU stays modest. A recording and dependency timings may reveal contention or connection waits rather than expensive Java computation.

Engineering decision synthesis

Choose a runtime and collector against workload and deployment limits. Compare warm steady-state behavior and startup separately; a microbenchmark rarely predicts full service latency.

Pitfall & diagnosis synthesis

Treating every pause as a GC problem can hide a slow database. Increasing heap can reduce some collection pressure while increasing footprint and changing pause behavior.

Improve & validate synthesis

Form a hypothesis, capture JFR plus service metrics, change one factor, then repeat representative load. Keep the measurement environment and warm-up conditions explicit.