Performance Testing - Interview Guide

I approach performance testing in three phases. First, baseline: profile the current system under normal load to establish response time, throughput, and resource utilization benchmarks. Second, load test: gradually increase concurrent users to find the breaking point and identify bottlenecks — I use k6 or Locust for this. Third, soak test: run sustained load for 24+ hours to catch memory leaks and connection pool exhaustion. I always test in an environment that mirrors production as closely as possible. In my last project, performance testing revealed a database connection leak that only manifested after 4 hours of sustained traffic. We fixed it before launch and avoided what would have been a production outage during our busiest period.