Performance Audit
by jamelna-apps
When the user mentions "slow", "performance", "optimize", "speed", "lag", "loading", "memory", "CPU", or asks to make something faster. Provides performance analysis framework.
Skill Details
Repository Files
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name: performance-audit description: When the user mentions "slow", "performance", "optimize", "speed", "lag", "loading", "memory", "CPU", or asks to make something faster. Provides performance analysis framework.
Performance Audit Framework
Initial Assessment Questions
- What's slow? - Page load, API response, build time, runtime
- How slow? - Quantify: 3s vs 30s matters
- Baseline? - What's acceptable performance?
- When? - Always slow, or under certain conditions?
- Where? - Client, server, network, database?
Measurement First
NEVER optimize without measuring. Identify bottlenecks before fixing.
Web Performance Metrics
- LCP (Largest Contentful Paint) - Main content visible
- FID (First Input Delay) - Interactivity
- CLS (Cumulative Layout Shift) - Visual stability
- TTFB (Time to First Byte) - Server response
Tools
- Chrome DevTools Performance tab
- Lighthouse audit
- WebPageTest.org
- React DevTools Profiler
console.time()/console.timeEnd()
Common Performance Issues
Frontend
| Issue | Detection | Fix |
|---|---|---|
| Large bundle | Webpack analyzer | Code splitting, tree shaking |
| Render blocking | Network waterfall | Defer/async scripts, critical CSS |
| Excessive re-renders | React Profiler | useMemo, useCallback, React.memo |
| Memory leak | Memory timeline | Cleanup effects, remove listeners |
| Layout thrashing | Performance timeline | Batch DOM reads/writes |
Backend/API
| Issue | Detection | Fix |
|---|---|---|
| N+1 queries | Query logs | Eager loading, batching |
| Missing indexes | EXPLAIN plans | Add appropriate indexes |
| No caching | Repeated queries | Redis, in-memory cache |
| Sync blocking | Flame graphs | Async/await, worker threads |
| Large payloads | Network tab | Pagination, field selection |
Database
| Issue | Detection | Fix |
|---|---|---|
| Full table scan | EXPLAIN | Add index on filter columns |
| Too many indexes | Write latency | Remove unused indexes |
| Large result sets | Memory usage | Pagination, streaming |
| Lock contention | Deadlock logs | Optimize transactions |
Quick Wins Checklist
Frontend:
- Enable gzip/brotli compression
- Set cache headers
- Lazy load images and routes
- Use production builds
- Minimize third-party scripts
Backend:
- Add database indexes for common queries
- Implement response caching
- Use connection pooling
- Enable query result caching
- Optimize N+1 queries
Performance Budget
Set limits and enforce:
- Bundle size: < 200KB (gzipped)
- API response: < 200ms (p95)
- Page load: < 3s (LCP)
- Build time: < 60s
Output Format
When reporting:
- Current State - Measured performance with numbers
- Bottlenecks - Identified issues ranked by impact
- Recommendations - Specific fixes with expected improvement
- Priority - Quick wins vs larger refactors
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