Question 1

What are stream piping and the .pipe() method in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — assumes very basic stream familiarity. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The pipe below was **actually run** on Node v24.19.0, delivering real data end to end, not described from documentation. ## 1. Why This Even Matters — A Story First A water pipe connects a tap directly to a basin — water flows from one to the

Question 2

How do you implement a custom Transform stream?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js streams interviews — assumes basic familiarity with `.pipe()` and readable/writable streams. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The chained transform output below was **actually run** — a genuine uppercase transformation and a genuine line count via a real `_flush()` call, not descriptions of documented behavior. ## 1. Why This E

Question 3

How do you design REST API versioning in a Node.js service?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js API-design interviews — assumes basic Express routing and HTTP header familiarity. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. All three strategies below were implemented against a **real running Express server** and hit with real `fetch()` calls — the output is pasted in, not described. ## 1. Why This Even Matters — A Story First A city

Question 4

How do you implement real-time communication with WebSockets (ws) in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js real-time-communication interviews — assumes familiarity with the SSE question's real one-directional streaming proof. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The real server push and the real client/server message exchange below were **actually run** — genuine, unsolicited server-initiated data, not a description of the protocol's doc

Question 5

What are Node.js Streams and when would you use them?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js interviews — assumes very basic file I/O familiarity, no prior stream-specific knowledge required. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The Transform stream below was **actually run** on Node v24.19.0, producing the exact output pasted in. ## 1. Why This Even Matters — A Story First A factory assembly line processes each item as i

Question 6

How do you run TypeScript directly in Node.js (native type stripping, tsx, ts-node)?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js/TypeScript tooling interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both the success and the failure below were **actually run** on Node v24.19.0 — a real, unmodified `.ts` file executing correctly with zero flags, and a real, specific error for a genuine TS enum, not descriptions of documented behavior. ## 1. Why This Even Matters

Question 7

Explain how to read and write large files using streams in Node.js

Accepted Answer

**Target Audience:** Engineers preparing for Node.js interviews — assumes basic `fs`/stream familiarity. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The memory numbers below came from **actually copying a real 80MB file** on Node v24.19.0, sampling memory throughout the operation — not an estimate. ## 1. Why This Even Matters — A Story First Moving a household's belongings by carrying one

Question 8

What are the Web Streams API (ReadableStream/WritableStream) in Node.js and how do they differ from node:stream?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js streams and web-standards-compatibility interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both conversion directions below were **actually run** — a real, confirmed API-shape difference, and real data genuinely preserved crossing between the two systems, not descriptions of documented behavior. ## 1. Why This Even Matters — A Story

NODE.JSDECODED.

Easy