Before release, run Lighthouse on mobile throttling, not just desktop. Many regressions only appear on low-end devices and slow networks.
Prioritize fonts and images: subset fonts, display swap, and image sizes matched to viewport. A full-bleed hero can still be fast if media sources are optimized.
Separate above-the-fold content from secondary data. Lazy-load sections below the viewport and avoid client-side fetch waterfalls without reason.
Measure Core Web Vitals in staging that mirrors production. Good local scores do not guarantee that CDN, cache, and remote APIs remain healthy.