Question 1

RSC vs Client Components — when do you add 'use client' in Next.js 15?

Accepted Answer

**Target Audience:** Engineers preparing for Next.js interviews — assumes what Server Components are. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** this needs an RSC runtime, and react-server-dom-webpack is **not installed here**, so nothing below was executed. **Version n

Question 2

Server Actions — how do mutations work without API routes in Next.js 15?

Accepted Answer

**Target Audience:** Engineers preparing for Next.js interviews — assumes what the directive does. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** this needs a running Next.js server and there is none here, so the workflow was **not executed**. The React-level pieces it builds

Question 3

Next.js instrumentation hook — observability in Next.js 15

Accepted Answer

**Target Audience:** Engineers preparing for Next.js interviews — assumes basic App Router knowledge. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** this could not be executed — there is no instrumentation file in this repo and no OpenTelemetry installed. What section 3 shows is **read directly from the type definitions shipped in the installed Next.js package**, so

Question 4

Partial Prerendering (PPR) in Next.js 15 — static shell + dynamic holes

Accepted Answer

**Target Audience:** Engineers preparing for senior React interviews — assumes SSR and Suspense. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** PPR is a Next.js build-and-serve feature and **cannot be executed in this environment** — there is no Next.js runtime here. Everything below is stated from the documented model rather than measured, and this doc says so rather

REACT.JSDECODED.

Medium

RSC vs Client Components — when do you add 'use client' in Next.js 15?

Server Actions — how do mutations work without API routes in Next.js 15?

Next.js instrumentation hook — observability in Next.js 15

Hard

Partial Prerendering (PPR) in Next.js 15 — static shell + dynamic holes