What is the difference between load testing, stress testing, and soak testing?
- load testing
- stress testing
- soak testing
- test types
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Load testing: simulate expected user traffic to verify the system meets performance SLAs under normal conditions. Stress testing: push beyond expected load to find the breaking point, what happens at 2x, 5x, 10x normal traffic. Soak (endurance) testing: run at normal load for an extended period (hours/days) to find memory leaks, connection pool exhaustion, and gradual degradation. Each answers a different question: "Can it handle normal load?" vs "When does it break?" vs "Does it degrade over time?"
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.