nextjs

Next.js App Router uses file-based routing to structure pages and layouts. Create files in the app directory—page.tsx for pages, layout.tsx for layouts wrapping multiple routes, and use folders to define route segments. This convention automatically generates your application's URL structure and enables nested layouts for shared UI.

Fetch data directly inside Server Components using async/await, eliminating client-side data loading waterfalls. Server Components execute on the server, reducing JavaScript sent to browsers. Use Server Actions for mutations and combine parallel data fetching to optimize performance without additional client libraries.

Yes. Next.js API route handlers in the app directory let you build backend endpoints alongside frontend code. Define handlers in route.ts files within api route segments, handle requests server-side, and return JSON responses. This enables fullstack development in a single codebase with TypeScript type safety.

Next.js 15+ optimizes through Server Components reducing client JavaScript, static rendering for fast page delivery, incremental static regeneration for dynamic content, and streaming for progressive page loading. Leverage loading and error boundaries to handle asynchronous operations gracefully and improve perceived performance.

Yes. Next.js App Router supports dynamic segments using [param] syntax for flexible routing and generateMetadata for SEO optimization. Define route parameters in filenames, generate metadata dynamically based on route data, and use route groups for organizing code without affecting URL structure.

Use Server Actions for mutations triggered from the client—they're simpler than API routes for form submissions and state updates. Use API routes when building public endpoints or integrating third-party services. Server Actions provide better TypeScript integration and reduced boilerplate for client-to-server communication.