Next.js

Next.js extends React with routing, rendering modes, caching, and production delivery. Strong interview answers name where code runs, how a route is rendered, what is cached, and which invalidation or authorization boundary protects correctness.

Child sections cover routing, rendering strategies, server/client boundaries, API surface, and production concerns. Framework defaults are not architecture — they are starting points you must justify per route.

On interviews: expect trade-off questions — App Router versus Pages Router, SSR versus SSG or ISR, Server Components versus Client Components, route handlers versus external APIs, and Vercel defaults versus custom Node hosting.

Common pitfalls: treating Next.js as "server-side React" without naming cache layers, putting secrets in client components, and using middleware for heavy backend work.

Checklist:

• Name the runtime for each route segment.
• Choose rendering and cache scope deliberately.
• Plan revalidation and auth boundaries.
• Connect SEO and latency to rendering choices.