We've been running Next.js 15 in production across 30+ client sites for several months now. The performance improvements are real and measurable. Here's our comprehensive benchmark data.
Server Components are the headline feature, and the impact on bundle size is dramatic. Across our portfolio, client-side JavaScript bundles shrank by 35-60%. One e-commerce site went from 280KB to 110KB of client JS — a 61% reduction.
The Partial Prerendering (PPR) feature combines static and dynamic content on the same page. Our SaaS landing pages using PPR achieve sub-100ms Time to First Byte (TTFB) for static content while still serving personalized dynamic sections.
Turbopack in development mode has transformed our workflow. Cold starts dropped from 8-12 seconds (webpack) to 1-3 seconds. Hot module replacement is near-instant. Developer experience improvements directly translate to faster iteration and higher quality output.
Image optimization with the built-in Image component continues to improve. Next.js 15's AVIF support and improved lazy loading reduced Largest Contentful Paint (LCP) by an average of 400ms across our sites.
Route Groups and Parallel Routes enable sophisticated layouts without client-side complexity. We've built dashboards with independently loading panels, reducing perceived load times by 50% compared to traditional approaches.
Streaming SSR with Suspense boundaries is a game-changer for data-heavy pages. Instead of waiting for all data before rendering, the page structure loads instantly while data streams in. Time to Interactive improved by 40% on our portfolio sites.
Edge Runtime deployment on Vercel puts rendering close to users globally. We measured TTFB improvements of 200-400ms for international traffic by deploying middleware and API routes to the edge.
Our recommendation: Next.js 15 is production-ready and the upgrade is worthwhile for any Next.js project. The Server Components migration requires effort but the performance gains justify the investment for any site where Core Web Vitals matter.