Why Web Performance Matters

Web performance directly impacts user experience, conversion rates, and search engine rankings. Google uses Core Web Vitals as ranking signals, making performance optimization an SEO imperative. At Nexis Limited, we build all our web applications with performance as a first-class design constraint.

Core Web Vitals Explained

Largest Contentful Paint (LCP)

LCP measures the time it takes for the largest visible content element to render. Target: under 2.5 seconds. Common LCP elements include hero images, heading text, and video thumbnails. Optimize by preloading critical resources, using responsive images with srcset, and server-side rendering above-the-fold content.

First Input Delay (FID) / Interaction to Next Paint (INP)

FID measures the delay from a user's first interaction to the browser's response. INP, which has replaced FID as a Core Web Vital, measures responsiveness throughout the page lifecycle. Target: under 200ms. Optimize by reducing JavaScript execution time, breaking long tasks into smaller chunks, and deferring non-critical scripts.

Cumulative Layout Shift (CLS)

CLS measures visual stability — how much the page content shifts during loading. Target: under 0.1. Prevent CLS by setting explicit width and height on images and videos, reserving space for dynamic content, and avoiding above-the-fold content injection.

Image Optimization

Images typically account for the largest portion of page weight. Optimization strategies include:

  • Use modern formats (WebP, AVIF) with fallbacks for older browsers.
  • Implement responsive images with srcset and sizes attributes.
  • Lazy-load images below the fold using loading="lazy".
  • Use Next.js Image component, which handles optimization, resizing, and format conversion automatically.

Code Splitting and Lazy Loading

Ship only the JavaScript needed for the current page. Next.js automatically splits code by route, but component-level splitting with dynamic imports can further reduce initial bundle sizes. Heavy libraries (chart libraries, rich text editors) should be loaded on demand.

Caching Strategy

Implement a multi-layer caching strategy:

  • CDN caching: Cache static assets at the edge with long cache durations and content-hash filenames for cache busting.
  • Browser caching: Set appropriate Cache-Control headers for different asset types.
  • Application caching: Use Redis for API response caching, database query caching, and session storage.

Server-Side Rendering and Static Generation

For content-heavy pages (blog posts, product pages), static generation at build time provides the fastest possible performance — the HTML is pre-built and served directly from a CDN. For dynamic pages, server-side rendering with streaming ensures fast initial page loads while data is fetched on demand.

Conclusion

Web performance is not a one-time optimization — it requires ongoing measurement and improvement. Monitor Core Web Vitals in production, set performance budgets, and treat regressions as bugs. The effort pays off in better user experience, higher search rankings, and improved conversion rates.

Want to optimize your website's performance? Let our team audit your site and implement improvements.