What key performance metrics should you monitor during a load test?
- metrics
- response time
- percentiles
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Response time (p50, p95, p99, not just average), throughput (requests per second), error rate (% of failed requests), concurrent users, and resource utilization (CPU, memory, disk I/O, network). p95 and p99 are more important than average - they show worst-case user experience. Also monitor: database query times, connection pool usage, queue depth, and garbage collection pauses.
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.