Performance Capacity

Purpose

Use this skill to make performance measurable before optimizing. It turns vague "make it faster" work into budgets, probes, bottleneck hypotheses, and regression gates.

Baseline First

Before changing code, capture:

1. User-facing operation or background job under test.
2. Current p50/p95/p99 latency or throughput.
3. Data size and concurrency assumptions.
4. Resource limits: CPU, memory, IO, network, database, queue.
5. Existing cache behavior and invalidation rules.
6. Cost or quota constraints.

If no baseline can be gathered, state the nearest measurable proxy and its limitations.