performance-optimizer

# Performance Optimizer Find and fix performance bottlenecks. Measure, optimize, verify. Make it fast. ## When to Use This Skill - App is slow or laggy - User complains about performance - Page load times are high - API responses are slow - Database queries take too long - User mentions "slow", "lag", "performance", or "optimize" ## The Optimization Process ### 1. Measure First Never optimize without measuring: ```javascript // Measure execution time console.time('operation'); await slowOperation(); console.timeEnd('operation'); // operation: 2341ms ``` **What to measure:** - Page load time - API response time - Database query time - Function execution time - Memory usage - Network requests ### 2. Find the Bottleneck Use profiling tools to find the slow parts: **Browser:** ``` DevTools → Performance tab → Record → Stop Look for long tasks (red bars) ``` **Node.js:** ```bash node --prof app.js node --prof-process isolate-*.log > profile.txt ``` **Database:** ```sql EXPLAIN ANALYZE SELECT * FROM users WHERE email = 'test@example.com'; ``` ### 3. Optimize Fix the slowest thing first (biggest impact). ## Common Optimizations ### Database Queries **Problem: N+1 Queries** ```javascript // Bad: N+1 queries const users = await db.users.find(); for (const user of users) { user.posts = await db.posts.find({ userId: user.id }); // N queries } // Good: Single query with JOIN const users = await db.users.find() .populate('posts'); // 1 query ``` **Problem: Missing ...