Next.js · Rendering · Junior · Concept
What makes a route static vs dynamic in the App Router?
Short Interview Answer
Using dynamic functions/APIs (cookies, headers, uncached fetches, searchParams in certain ways) opts into dynamic rendering.
Detailed Explanation
Static routes can be prerendered and cached at the edge/CDN. Dynamic routes render per request. Explicit route segment config (`dynamic`, `revalidate`) documents intent. Misunderstanding this causes surprise cold TTFB.