Question 1

What is `create-react-app` and when would you use it?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes you have started a React project before. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The deprecation status below was checked against the React team announcement rather than recalled — this is a topic where an out-of-date answer is very visible, so the source is cited inline. ## 1. Why This Even Matters — A Story First <

Question 2

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 3

How do you fetch data in React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes useEffect. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. This doc is the decision landscape; async operations covers the mechanics and race conditions, and

Question 4

How do you handle routing in React applications?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — no prior routing knowledge assumed. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** no client router is installed in this repo — routing here is Next.js's file-based App Router (**16.3.4** installed) — so no router API was executed. The **data-loading measurements** the argument turns on were executed and

Question 5

Async Server Components & waterfall prevention — fetching without blocking

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes Server Components basics. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** unlike most docs in this set, the behaviour here cannot be executed in a unit environment — Server Components need a server runtime and a bundler that understands the RSC protocol. Everything below is reasoned from the docum

Question 6

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 7

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 8

Error Boundaries with RSC — why can't Server Components catch errors?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes error boundaries and Server Components. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** this repo has **no RSC runtime** — r

Question 9

Suspense streaming in React 19 & Next.js 15 — how does HTML stream?

Accepted Answer

With `renderToPipeableStream` (and Next.js App Router), React streams HTML in chunks: the shell (layout, nav) flushes immediately, each `` boundary streams its.

Question 10

What is server-side rendering (SSR) and when would you use it with React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — no prior SSR experience assumed. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every server-render output below was **executed against React 19.2.8** using react-dom/server; the raw output is in sections 3 and 5. The companion docs are CSR vs

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