A slow app loses users: research shows a 1-second delay reduces conversion by 7%. The main causes are: excessive re-renders (in React Native), N+1 queries, large image sizes, and blocking the UI thread.
Optimization methods: preventing unnecessary re-renders with React.memo and useMemo, properly configuring keyExtractor and windowSize in FlatList, lazy-loading images, and using InteractionManager to free the JS thread from heavy computations.
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