Performance Profiler and Optimizer

Analyze this code for performance issues and optimize:

1. Identify unnecessary re-renders in React components
   - Add React.memo() where props are stable
   - Use useMemo() for expensive computations
   - Use useCallback() for functions passed as props
2. Find O(n²) or worse algorithms and suggest O(n) alternatives
3. Identify missing database indexes (if SQL queries present)
4. Find N+1 query problems and suggest batching/joins
5. Check for memory leaks (uncleared intervals, event listeners, subscriptions)
6. Suggest code splitting and lazy loading opportunities
7. Identify blocking operations that should be async
8. Check for unnecessary data copying (spread in loops, array concat in loops)
9. Suggest caching strategies where data is fetched repeatedly

For each issue found:
- Explain the performance impact
- Show the fix with before/after
- Estimate the improvement (qualitative is fine)