How do you approach a performance problem methodically?

Summary

Define the goal and measure (which metric, which percentile, under what load), reproduce, profile to find where time is actually spent (traces, CPU/memory profilers, query analysis), fix the biggest bottleneck, and re-measure, repeating until the goal is met.

Longer Answer

Avoid optimizing by intuition. Common culprits: database queries (N+1, missing indexes), external calls in series, chatty network round trips, serialization of big payloads, lock contention, GC pressure and synchronous work that could be async or cached.

Key Points

• Set measurable goals
• Profile, don't guess
• Fix the biggest bottleneck
• Re-measure