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Clear filtersA component re-renders when its state changes, its parent re-renders, or a context it consumes changes; you prevent wasted renders by moving state down, using React.memo, and keeping props referentially stable.
Measure first with the Profiler and Lighthouse, then reduce unnecessary renders, split code with lazy loading, virtualise long lists, and optimise images and bundle size.
Core Web Vitals are Google鈥檚 field metrics for real-user experience: LCP (loading), INP (interactivity) and CLS (visual stability). They influence search ranking and are measured on real devices, not only Lighthouse.
Keep the main thread free by moving CPU-heavy work to worker threads or a job queue, and scale across cores and machines by running multiple processes (cluster or PM2) behind a load balancer with shared, external state.
Read the execution plan with EXPLAIN to find full scans and expensive joins, add or fix indexes for the filter and join columns, select only the columns and rows you need, and rewrite predicates so indexes can be used.