performance-fundamentalslisted

# Performance Fundamentals Review > "Premature optimization is the root of all evil, but mature ignorance is worse." ## When to Apply Activate this skill when reviewing: - Database queries (especially in loops) - React/Vue render logic - API response payloads - Data transformations - File operations - Caching decisions --- ## Review Checklist ### Database Performance - [ ] **No N+1 queries**: Are related records fetched in bulk, not loops? - [ ] **Indexes**: Are frequently queried fields indexed? - [ ] **Pagination**: Do list endpoints paginate results? - [ ] **Select only needed fields**: Are we fetching entire records unnecessarily? ### Frontend Performance - [ ] **Memoization**: Are expensive computations cached? - [ ] **Re-render prevention**: Will state changes cause unnecessary re-renders? - [ ] **Bundle size**: Are heavy libraries lazy-loaded? - [ ] **Image optimization**: Are images properly sized and formatted? ### API Performance - [ ] **Response size**: Is the payload minimal? - [ ] **Compression**: Is gzip/brotli enabled? - [ ] **Caching headers**: Are cacheable responses marked? - [ ] **Async processing**: Are slow operations queued? ### Memory & Resources - [ ] **Cleanup**: Are subscriptions/timers cleaned up? - [ ] **Memory leaks**: Are event listeners removed? - [ ] **Connection pooling**: Are DB connections reused? --- ## Common Mistakes (Anti-Patterns) ### 1. The N+1 Query Problem ``` ❌ const users = await User.findAll(); for (const user o