Building Performant Web Applications

Performance is crucial for user experience and SEO. Let’s explore key techniques for building fast web applications.

Why Performance Matters

• User Experience - Fast sites keep users engaged
• SEO Rankings - Google favors fast-loading sites
• Conversion Rates - Speed directly impacts business metrics
• Accessibility - Performance benefits all users, especially those on slow connections

Core Web Vitals

Focus on these key metrics:

Largest Contentful Paint (LCP)

• Target: Under 2.5 seconds
• Measures loading performance
• Optimize images and server response time

First Input Delay (FID)

• Target: Under 100ms
• Measures interactivity
• Minimize JavaScript execution time

Cumulative Layout Shift (CLS)

• Target: Under 0.1
• Measures visual stability
• Reserve space for dynamic content

Optimization Techniques

1. Code Splitting

Split your code into smaller chunks that load on demand:

// Dynamic import
const module = await import('./heavy-module.js');

2. Image Optimization

• Use modern formats (WebP, AVIF)
• Implement lazy loading
• Serve responsive images

<img
  src="image.jpg"
  loading="lazy"
  srcset="image-320w.jpg 320w, image-640w.jpg 640w"
  alt="Description"
/>

3. Caching Strategies

Implement effective caching:

• Use service workers for offline support
• Set appropriate cache headers
• Implement stale-while-revalidate

4. Minimize JavaScript

• Remove unused code
• Tree shake dependencies
• Use modern build tools

Measuring Performance

Tools to measure and monitor:

• Lighthouse - Comprehensive audits
• WebPageTest - Detailed analysis
• Chrome DevTools - Real-time profiling

Conclusion

Performance optimization is an ongoing process. Start with the biggest wins and iterate based on real-world data.