Q: How do you read request data and return responses in a Next.js Route Handler?

A handler receives a standard Request : use await request.json() / formData() , request.nextUrl.searchParams , cookies() , and headers() . Return a Response or NextResponse (e.g. NextResponse.json(data, { status }) ). Dynamic **params** come from the **second argument**. <svg class='iq-diagram' viewBox='0 0 460 150' role='img' aria-label='Handler reads body/query/params and returns a Res

Question 1

How do metadata files like favicon.ico, icon, opengraph-image and manifest work in Next.js?

Accepted Answer

**Target Audience:** Beginners preparing for Next.js interviews — basic HTML (what the head element is) helps.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against a lab app built with `next build`, served with `next start` and inspected with `curl`.

## 1. Why This Even Matters — A

Question 2

What is not-found.js in Next.js and how do you trigger a 404?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against real output from a build, a running server or a real browser.

## 1. Why This Even Matters — A Story First

Question 3

What is Draft Mode in Next.js and how does it work with a headless CMS?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Medium

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against real output from a build, a running server or a real Chromium browser. **No real CMS was used:** the lab

Question 4

How do you read cookies and headers in Next.js (cookies(), headers())?

Accepted Answer

**Target Audience:** Developers preparing for Next.js interviews — assumes basic App Router knowledge (Server Components, Server Actions).
**Difficulty:** Medium

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against lab builds, `curl` requests to `next start` and a Chromium browser.

## 1. Why This Even

Question 5

What is Middleware in Next.js and what can it do?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Medium

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified bloc

Question 6

How do you handle redirects and rewrites in Next.js?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Medium

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified bloc

Question 7

How do Server Actions differ from Route Handlers in Next.js?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Medium

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified bloc

Question 8

PPR vs ISR vs SSR — how do you pick the rendering strategy in Next 15?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Medium

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified bloc

Question 9

How do you read request data and return responses in a Next.js Route Handler?

Accepted Answer

A handler receives a standard Request: use await request.json()/formData(), request.nextUrl.searchParams, cookies(), and headers(). Return a Response or NextResponse (e.g. NextResponse.json(data, { status })). Dynamic **params** come from the **second argument**.

Question 10

What are Route Handlers in Next.js and how do they differ from Pages API routes?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Medium

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified bloc

NEXT.JSDECODED.

Easy

How do metadata files like favicon.ico, icon, opengraph-image and manifest work in Next.js?

What is not-found.js in Next.js and how do you trigger a 404?

Medium

What is Draft Mode in Next.js and how does it work with a headless CMS?

How do you read cookies and headers in Next.js (cookies(), headers())?

What is Middleware in Next.js and what can it do?

How do you handle redirects and rewrites in Next.js?

How do Server Actions differ from Route Handlers in Next.js?

PPR vs ISR vs SSR — how do you pick the rendering strategy in Next 15?

How do you read request data and return responses in a Next.js Route Handler?

What are Route Handlers in Next.js and how do they differ from Pages API routes?

Hard

What are Server Actions in Next.js and how do they work?

What is Partial Prerendering (PPR) in Next.js?

What is the RSC payload and how does Next.js stream it to the browser?

What is the Router Cache in Next.js and what are its implications?

How do you implement dynamic Open Graph images in Next.js (ImageResponse)?

What are intercepting routes in Next.js and what are they used for?

`cacheLife` and `cacheTag` — how do you configure TTL profiles?

How do you stream responses and Server-Sent Events from a Route Handler?