Siyam Mahdi — Engineering Scalable Digital Systems

Performance Is a Feature

A fast website isn't a nice-to-have. It directly impacts conversion rates, SEO rankings, and user satisfaction. Here's how to systematically improve your Lighthouse score.

Core Web Vitals

Focus on the three metrics that matter:

LCP (Largest Contentful Paint) < 2.5s

Preload critical images

Use responsive image formats (WebP, AVIF)

Optimize server response time

Remove render-blocking resources

FID / INP (Interaction to Next Paint) < 200ms

Break up long tasks

Use web workers for heavy computation

Defer non-critical JavaScript

Optimize event handlers

CLS (Cumulative Layout Shift) < 0.1

Set explicit dimensions for images and videos

Reserve space for dynamic content

Avoid inserting content above existing content

Use CSS containment

Image Optimization

Images are typically the biggest performance bottleneck:

html

<Image
  src="/hero.jpg"
  alt="Hero image"
  width={1200}
  height={600}
  priority
  sizes="(max-width: 768px) 100vw, 80vw"
/>

Use Next.js Image component for automatic optimization, lazy loading, and responsive sizing.

Code Splitting

Don't ship code users don't need:

Dynamic imports for route-based splitting

React.lazy for component-level splitting

Tree shaking for unused exports

Bundle analysis to find hidden bloat

Font Optimization

Fonts can block rendering:

Use `next/font` for automatic optimization

Subset fonts to include only needed characters

Use `font-display: swap` for immediate text rendering

Preload critical fonts

Measuring and Monitoring

Set up continuous performance monitoring:

Lighthouse CI in your deployment pipeline

Real User Monitoring (RUM) for field data

Performance budgets to prevent regression

Regular audits and optimization sprints

Performance is not a one-time fix. It's an ongoing discipline that requires measurement, monitoring, and continuous improvement.

Performance Optimization: From 60 to 100 Lighthouse