Next.js App vs Pages Router Latency Estimator.

## The Streaming Revolution

The fundamental architectural shift in Next.js 13+ is React Server Components (RSC) and HTML Streaming.

In traditional SSR (Pages router), the server blocks the response until all data is fetched (`getServerSideProps`), then ships a massive JSON object to the client so React can hydrate. With RSC, server components render natively on the server and never ship their dependencies or data states to the client over the wire, resulting in instant shell renders and massive reduction in bundle size.