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 you handle file uploads in Next.js with Server Actions and Route Handlers?

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. Files were written to local disk i

Question 2

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 3

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 4

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

Question 5

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

Accepted Answer

**Target Audience:** Full-stack engineers preparing for senior Next.js interviews — assumes Route Handler basics and some familiarity with HTTP.
**Difficulty:** Hard

> **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 (the Route Handler reference and the streaming guide) and, in the **Verified** section, against real chunk timings from `curl -

NEXT.JSDECODED.

Medium

How do you handle file uploads in Next.js with Server Actions and Route Handlers?

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

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

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