Routing

Next.js routing interviews test whether you understand the file-system route tree, not only that folders become URLs. App Router is the modern default; Pages Router knowledge still matters for legacy codebases and migration discussions.

Subtopics: App Router layouts and segments, Pages Router legacy APIs, dynamic segments, route groups, and edge middleware.

On interviews: walk through nested layouts, when route groups change organization without changing URLs, and where middleware should stop versus route handlers.

Common pitfalls: confusing route groups with URL prefixes, overusing middleware, and ignoring dynamic param validation.

Checklist:

• Map folders to URL segments and layouts.
• Know dynamic and catch-all conventions.
• Separate middleware from route handlers.
• Plan not-found and error boundaries.