How do you perform capacity planning based on load test results?
- capacity planning
- growth modeling
- scalability
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Process: (1) Establish current capacity, what load does the system handle within SLA thresholds? (2) Model growth - if traffic is growing 20% quarterly, when will current capacity be exceeded? (3) Test scaling scenarios - does adding 2x instances give 2x capacity (linear scaling) or less (bottleneck elsewhere)? (4) Identify the constraint - DB, network, CPU, or specific service. (5) Build a capacity model: users × avg requests per session × peak multiplier = required throughput. Re-validate quarterly.
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.