# Performance Guidelines > Optimization strategies and best practices for frontend and backend performance. ## 🚀 Frontend Performance ### JavaScript Performance #### Bundle Optimization - **Code Splitting**: Split code into smaller chunks - **Tree Shaking**: Remove unused code from bundles - **Module Loading**: Use dynamic imports for non-critical code ```javascript // Dynamic imports for better performance const LazyComponent = lazy(() => import('./LazyComponent.js')); // Code splitting by route const AdminPanel = lazy(() => import('./admin/AdminPanel.js')); ``` #### Runtime Performance - **Debouncing/Throttling**: Limit expensive operations - **Virtual Scrolling**: Handle large datasets efficiently - **Memory Management**: Prevent memory leaks ```javascript // Debounced search const debouncedSearch = debounce((query) => { performSearch(query); }, 300); // Throttled scroll handler const throttledScroll = throttle(() => { updateScrollPosition(); }, 16); // ~60fps ``` ### CSS Performance #### Critical CSS - Inline critical CSS for above-the-fold content - Load non-critical CSS asynchronously - Use CSS containment for performance isolation ```css /* Critical CSS - inline in */ .hero-section { contain: layout style paint; /* Critical styles only */ } /* Non-critical CSS - load async */ @import url('non-critical.css') (min-width: 768px); ``` #### Efficient Selectors - Avoid complex selector chains - Use class selectors over tag selectors - Minimize reflows and repaints ```css /* Efficient */ .card-title { color: var(--text-primary); } /* Inefficient */ .card .content .title h2 { color: var(--text-primary); } ``` ### Asset Optimization #### Image Optimization - Use appropriate formats (WebP, AVIF) - Implement responsive images - Add loading="lazy" for below-fold images ```html

``` #### Font Loading - Use font-display: swap - Preload critical fonts - Subset fonts to reduce file size ```css @font-face { font-family: 'Inter'; font-display: swap; src: url('inter-subset.woff2') format('woff2'); } ``` ## ⚡ Backend Performance ### Database Optimization #### Query Optimization - Use indexes effectively - Avoid N+1 queries with eager loading - Implement connection pooling ```php // Eager loading to prevent N+1 $users = $userRepository->findWithProfiles(); // Use database indexes $users = $userRepository->findByEmailIndex('user@example.com'); ``` #### Caching Strategies - Redis for session and cache storage - Database query result caching - Fragment caching for expensive operations ```php // Cache expensive operations $result = $cache->remember('expensive-calculation', 3600, function() { return performExpensiveCalculation(); }); ``` ### HTTP Performance #### Response Optimization - Enable gzip/brotli compression - Set appropriate cache headers - Use CDN for static assets ```php // Set cache headers $response->headers->set('Cache-Control', 'public, max-age=3600'); $response->headers->set('ETag', $etag); ``` #### Connection Management - HTTP/2 server push for critical resources - Connection keep-alive - Reduce HTTP requests through bundling ## 📊 Performance Monitoring ### Metrics Collection #### Core Web Vitals - **LCP**: Largest Contentful Paint < 2.5s - **FID**: First Input Delay < 100ms - **CLS**: Cumulative Layout Shift < 0.1 ```javascript // Measure Core Web Vitals import { getCLS, getFID, getLCP } from 'web-vitals'; getCLS(console.log); getFID(console.log); getLCP(console.log); ``` #### Custom Metrics - Time to Interactive (TTI) - First Contentful Paint (FCP) - Resource loading times ```javascript // Custom performance marks performance.mark('feature-start'); // ... feature implementation performance.mark('feature-end'); performance.measure('feature-load', 'feature-start', 'feature-end'); ``` ### Performance Budget #### Resource Budgets - JavaScript: < 170KB gzipped - CSS: < 50KB gzipped - Images: < 500KB per page - Total page weight: < 1MB #### Timing Budgets - First Byte: < 600ms - First Contentful Paint: < 1.5s - Largest Contentful Paint: < 2.5s - Time to Interactive: < 3.8s ## 🔧 Tools & Testing ### Development Tools - **Lighthouse**: Automated performance auditing - **WebPageTest**: Real-world performance testing - **Chrome DevTools**: Performance profiling ### Continuous Monitoring - **Real User Monitoring (RUM)**: Actual user performance data - **Synthetic Monitoring**: Automated performance tests - **Performance Budgets**: CI/CD integration ```javascript // Performance budget in CI const budget = { resourceSizes: [ { resourceType: 'script', budget: 170 }, { resourceType: 'total', budget: 1000 } ], resourceCounts: [ { resourceType: 'third-party', budget: 10 } ] }; ``` ## 🎯 Optimization Checklist ### Frontend Checklist - [ ] Critical CSS inlined - [ ] JavaScript code split and lazy loaded - [ ] Images optimized and responsive - [ ] Fonts preloaded and optimized - [ ] Service Worker implemented - [ ] Performance metrics tracked ### Backend Checklist - [ ] Database queries optimized - [ ] Caching strategy implemented - [ ] HTTP compression enabled - [ ] CDN configured for static assets - [ ] Database connections pooled - [ ] Server monitoring active ### Monitoring Checklist - [ ] Core Web Vitals tracked - [ ] Performance budgets defined - [ ] Real User Monitoring active - [ ] Automated performance tests in CI - [ ] Performance regression alerts set up ## 📈 Performance Patterns ### Progressive Enhancement Build for performance from the ground up: 1. **Content First**: HTML loads fast 2. **Style Enhancement**: CSS loads progressively 3. **Interaction Layer**: JavaScript enhances experience 4. **Advanced Features**: Load only when needed ### Performance-First Architecture - Minimal initial bundle size - Lazy loading for secondary features - Service Worker for offline functionality - Resource prioritization for critical path --- *For specific framework optimizations, see [Framework Performance](../framework/performance/README.md)* *For monitoring setup, see [Analytics System](../framework/analytics/README.md)*