Lucas and Luna dive into the hidden cost of JavaScript framework updates on Core Web Vitals. Using the real-world case of a mid-size e-commerce site that saw its Largest Contentful Paint (LCP) jump from 2.1 seconds to 4.7 seconds after a routine React 18 to React 19 migration, they unpack what actually happened under the hood. They walk through the specific culprits: concurrent rendering introducing layout thrashing, a third-party analytics script that ballooned from 12KB to 89KB, and how the new Suspense boundaries triggered waterfalls that the old code didn't. Lucas explains why many teams miss performance regressions in staging environments, and Luna shares a practical tip about using Lighthouse CI in pull requests as a safety net. The episode also touches on when to resist framework upgrades and how to audit dependencies for invisible bloat. A must-listen for any frontend developer dealing with slow sites after an upgrade.

#WebVitals #CoreWebVitals #JavaScript #React #Performance #LCP #Frontend #WebDev #FrameworkUpgrade #React19 #Lighthouse #CI #ThirdPartyScripts #Suspense #ConcurrentRendering #Technology #FexingoBusiness #BusinessPodcast

Keep every episode free: buymeacoffee.com/fexingo