What is the difference between load testing, stress testing, and spike testing?
- load testing
- stress testing
- spike testing
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Load testing: measure performance under expected user volume (e.g., 1000 concurrent users). Stress testing: push beyond expected limits to find the breaking point (e.g., ramp to 10,000 users until errors appear). Spike testing: sudden burst of traffic (e.g., 0 to 5000 users in 10 seconds) to test auto-scaling and recovery. Each answers a different question: "Can we handle normal traffic?" vs. "When do we break?" vs. "Can we handle sudden surges?"
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.