Diagnose and fix performance bottlenecks across React frontends and database backends.

• Covers frontend optimization: React.memo, useMemo, useCallback, lazy loading, code splitting, image optimization, and bundle analysis
• Includes backend strategies: N+1 query fixes, database indexing, Redis caching, and API compression
• Provides measurement tools and workflows using Lighthouse, Web Vitals, and webpack-bundle-analyzer
• Emphasizes profiling first, incremental improvements, and continuous monitoring with performance regression tests