How do you test the performance of a database-heavy application?
- database performance
- query optimization
- connection pooling
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Beyond HTTP load testing, directly test the database layer: (1) Query performance, EXPLAIN plans for critical queries, index coverage. (2) Connection pooling - test pool exhaustion under load. (3) Read/write ratio - mirror production patterns. (4) Data volume - test with production-scale data (not a tiny dev DB). (5) Lock contention - concurrent updates to the same rows. (6) Replication lag - test read-replica consistency under write-heavy load. Monitor: query time percentiles, connection wait time, deadlock frequency.
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.