How do you read and set cookies in the 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
On the server (server components or route handlers) use cookies() from next/headers to read cookies. To set cookies from a route handler, return a Response with a Set-Cookie header or use a helper library in API routes.
// server component
import { cookies } from "next/headers";
const cookieStore = cookies();
const token = cookieStore.get("token")?.value;
// route handler (set cookie)
export function GET() {
return new Response("ok", {
headers: { "Set-Cookie": "token=abc; HttpOnly; Path=/" },
});
}
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.