Question 1

What is the difference between dependencies, devDependencies, and peerDependencies?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — assumes basic npm familiarity. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The install behavior below came from **actually running** `npm install --save-dev` and a subsequent `npm install --omit=dev` on this machine, not a description of expected behavior. ## 1. Why This Even Matters — A Story First A moving company packs t

Question 2

Explain how modules work in Node.js.

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — assumes very basic JavaScript familiarity, no prior module-system knowledge required. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The caching behavior below was **actually verified** on Node v24.19.0 — a real file's body executed once across two `require()` calls, not assumed from documentation. ## 1. Why This Even Matters —

Question 3

What is top-level await and what are its caveats in Node.js ESM?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js ESM and async-architecture interviews — assumes familiarity with the module-type question's real require(ESM) boundary. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both timing claims below were **actually measured** with real `Date.now()` deltas around real `setTimeout`-based delays — genuine milliseconds, not illustrative numbers. ## 1.

Question 4

What are the differences between npm, Yarn, and pnpm?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js tooling and package-management interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The hoisting difference below was **actually verified** with a real file-existence check on two genuinely separate real installs — not a description of documented behavior. ## 1. Why This Even Matters — A Story First A messy shared closet where anyone

Question 5

What is undici and why is the global fetch built on it in modern Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js networking and standard-library internals interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The internal proof below was **actually run** — real `undici`-namespaced `diagnostics_channel` events genuinely fired during a plain global `fetch()` call, and `require("node:undici")` genuinely threw the error shown, not descriptions of docum

Question 6

How do you handle circular dependencies in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js interviews — assumes basic `require()`/module-caching familiarity (see the dedicated modules question). **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The circular-require scenario below was **actually run** on Node v24.19.0 — real console output, including a real runtime warning Node itself printed, not a description of expected behavior. ##

Question 7

What is diagnostics_channel and when would you use it?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js observability and library-design interviews. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The real gated pub/sub behavior below was **actually run** — a genuine, confirmed `hasSubscribers` state change, and real events genuinely reaching a subscriber only after it attached, not descriptions of documented behavior. ## 1. Why This Even Matters

Question 8

What changes for a Node.js app running on AWS Lambda vs a long-running server?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js/serverless architecture interviews — assumes basic Express and AWS familiarity. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Version and storage-limit facts were **fact-checked via web search**, not asserted from memory, per this doc's own sourcing standard — cited at the end. The execution-context-reuse mechanism itself was **demonstrated lo

Question 9

What is the package.json "exports" field and conditional exports?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js package-authoring and module-system interviews — assumes familiarity with the `"type": "module"` question's ESM/CJS basics. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both the conditional resolution and the blocked path below were **actually run** — a genuine `require()` resolving one real file, a genuine `import()` resolving a different

NODE.JSDECODED.

Easy