React Performance: From Good to Great

The Performance Mindset

Performance optimization starts with measurement. Before you optimize anything, profile your application to find the actual bottlenecks.

Quick Wins

• React.memo — Prevent unnecessary re-renders
• useMemo / useCallback — Memoize expensive computations and callbacks
• Code Splitting — Use dynamic imports with React.lazy
• Image Optimization — Use next/image or responsive images

Advanced Techniques

Virtual Lists For large lists, use virtualization libraries like react-window. We reduced a 10,000-row table from 3s render to 16ms.

Web Workers Offload heavy computations to Web Workers. JSON parsing, data transformation, and complex calculations should never block the main thread.

Concurrent Features React 18's concurrent features like useTransition and useDeferredValue let you keep the UI responsive during heavy updates.

Measuring Impact

Always measure before and after optimization. Use React DevTools Profiler, Lighthouse, and Web Vitals to track improvements.

Conclusion

Don't optimize prematurely, but don't ignore performance either. Profile, optimize the bottlenecks, and verify the improvement.