React Performance Optimisation: 10 Patterns Senior Devs Use

React performance problems have a signature. The app feels fine in development, snappy on your MacBook Pro, then gets to a real user on a mid-range Windows laptop or an Android phone in Texas, and suddenly it's sluggish. The fixes aren't magic. They're patterns. Specific, repeatable, applicable to most React codebases. Here are the ten I reach for most often when profiling real production applications for US clients. 1. Profile First, Optimise Second This sounds obvious until you see how many teams optimise by intuition rather than data. React DevTools Profiler is free and ships with the browser extension. Use it before touching any code. Open the Profiler tab, hit Record, reproduce the slowness, stop recording. You'll see a flame graph of every component render with its duration. The wide, tall bars are your targets. Only optimise what shows up here. Premature optimisation is real and it makes codebases harder to maintain for no benefit. 2. useMemo for Expensive Calculations // Proble