How do you handle not-found pages in App Router?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of Next.js conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
You can create custom not-found pages using the not-found.js file. This file defines UI to render when the notFound() function is thrown within a route segment.
// app/not-found.js
import Link from "next/link";
export default function NotFound() {
return (
<div>
<h2>Not Found</h2>
<p>Could not find requested resource</p>
<Link href="/">Return Home</Link>
</div>
);
}
You can also trigger the not-found page programmatically:
// app/page.js
import { notFound } from "next/navigation";
export default function Page({ params }) {
const post = getPost(params.id);
if (!post) {
notFound();
}
return <div>{post.title}</div>;
}
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.