nextjs

Next.js has multiple caching layers — Request Memoization deduplicates identical fetches in a single render, the Data Cache persists fetch results across requests, the Full Route Cache stores rendered HTML/RSC payload at build time, and revalidation (time-based or on-demand) controls when cached data refreshes.

Next.js middleware runs before every request at the edge — defined in a single middleware.ts file at the project root, it can redirect, rewrite, set headers/cookies, and return responses, using a limited edge runtime without Node.js APIs like fs or native modules.

Next.js provides automatic code splitting per route, next/dynamic for lazy-loading heavy components, streaming with Suspense for progressive page loading, Server Components for zero-client-JS rendering, and bundle analysis tools — together these techniques minimize JavaScript sent to the browser.

Next.js supports four rendering strategies — Static (SSG) generates HTML at build time for fastest delivery, Dynamic (SSR) renders per request for fresh data, ISR revalidates static pages on a timer, and Streaming sends HTML progressively with Suspense — the App Router automatically determines the strategy based on your code.

Server Actions are async functions marked with 'use server' that run exclusively on the server — they replace API routes for mutations (form submissions, data updates), support progressive enhancement (forms work without JavaScript), and integrate with React's useActionState and useOptimistic for pending/optimistic UI.