Careeroza
Real World Example
Fixing a Slow Product Page
A typical audit on an Indian D2C store (tested on a mid-range Android over 4G) and the fixes applied in Next.js:
| Problem found | Fix | Result |
|---|---|---|
| LCP 4.8 s: hero image 1.9 MB JPEG, lazy loaded | next/image + priority + sizes | LCP 2.1 s |
| CLS 0.28: font swap and banner without height | next/font, fixed aspect-ratio box | CLS 0.02 |
INP 420 ms: 380 KB JS, whole page 'use client' | Server Components, client only for cart/gallery | JS 140 KB, INP 150 ms |
| Chat widget blocks main thread | strategy="lazyOnload" | TBT −300 ms |
| Reviews query 900 ms blocks page | <Suspense> streaming | TTFB 180 ms |
Lighthouse Before and After
Example
npx lighthouse https://shopease.in/products/42 --only-categories=performance --form-factor=mobile --quiet --output=json | jq ".categories.performance.score"Example output
before: 0.41 after: 0.93