Performance Tuning

Intuition about where time goes is wrong more often than it is right. You measure the problem, profile to find where the time or memory actually goes, change one thing, and measure again with the same method. No measurement, no optimisation: every change is justified by a number before and proven by a number after.

The Prime Directive

NO OPTIMISATION WITHOUT A MEASUREMENT PROVING THE PROBLEM

No exceptions. No workarounds. No shortcuts.

When to Use

Required:

• A user, test or monitor reports slowness, timeouts, high memory, large bundles or high cost.
• A performance budget or target is breached (latency percentile, Core Web Vitals, bundle size, query time, cold start).
• Someone asks to "optimise", "speed up" or "make it scale".
• You are about to add a cache, an index, concurrency, a rewrite in another language or a micro-optimisation.