How do you identify performance bottlenecks from load test results?
- bottleneck analysis
- APM
- troubleshooting
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Systematic approach: (1) Correlate response time degradation with resource metrics, does CPU spike when response times increase? (2) Check database - slow queries (enable slow query log), connection pool exhaustion, lock contention. (3) Check application - thread pool saturation, memory leaks (heap growth over time), GC pauses. (4) Check infrastructure - network bandwidth, disk I/O, load balancer distribution. (5) Use APM tools (Datadog, New Relic) to trace individual slow requests through the stack.
What interviewers listen for
- Workload modellingYou design the load shape from product traffic, not from tool defaults.
- Percentile literacyYou read p50/p95/p99 separately and explain why each matters.
- Bottleneck triageYou correlate metrics across application, database, and infrastructure layers.
- Capacity instinctsYou can translate a soak test into a sizing or scaling recommendation.