Question 1

How do you run Node.js processes as a background service?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js/DevOps phone screens — assumes very basic `child_process`/Unix process familiarity. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The detached-process survival below was **actually run** on this machine, with a real log file confirming the child kept working after its parent had already exited. ## 1. Why This Even Matters — A Story First A c

Question 2

What does NODE_ENV=production actually change and why does it matter?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js deployment and configuration interviews. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both the "Node core does nothing special" proof and the real Express behavior difference below were **actually run** — not descriptions of documented behavior. ## 1. Why This Even Matters — A Story First A single word written on a sticky note ("PRODUCTION"

Question 3

How do you handle environment variables in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — no prior configuration-management experience assumed. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The string-coercion behavior below was **actually verified** on Node v24.19.0, not assumed from how JavaScript "usually" handles types. ## 1. Why This Even Matters — A Story First A form field that only accepts typed text will

Question 4

How do you manage configuration in a Node.js application for different environments?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js interviews — assumes basic `process.env` familiarity. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The config-switching behavior below was **actually run** across three different `NODE_ENV` values on Node v24.19.0, including the failure case. ## 1. Why This Even Matters — A Story First A single stage play script works in two different the

Question 5

How do you containerize a Node.js app with a small, secure Docker image (multi-stage, distroless)?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js deployment/DevOps-adjacent system-design interviews. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The production-vs-full dependency size gap below was **actually measured** in this sandbox via real `npm install` runs. The full Docker image build itself could not be executed in this particular sandbox session (Docker Desktop's engine was not

Question 6

How do you implement Server-Sent Events (SSE) in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js real-time-communication interviews — assumes familiarity with the WebSockets question's real bidirectional proof. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The real events below were **actually streamed** from a real server to a real client over one connection — genuine timestamps roughly 100ms apart, not a single buffered response. ##

Question 7

How do you implement rate limiting in a Node.js Express application?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js/Express interviews — assumes basic Express middleware familiarity. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The rate-limiter behavior below was **actually run** against a real Express server on Node v24.19.0 — real status codes and real header values, directly answering the prompt's own request to verify it. ## 1. Why This Even Matters

Question 8

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 9

What is PM2 and what does it add over running `node server.js` directly?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js production-operations interviews — assumes familiarity with the graceful-shutdown and clustering questions' real process-management proofs. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The restart behavior below was **actually run** — a real crashing script, a real PM2 daemon, real distinct PIDs captured from real logs — not a description o

Question 10

Explain how clustering works in Node.js.

Accepted Answer

**Target Audience:** Engineers preparing for Node.js system-design interviews — assumes familiarity with the single-thread concurrency model from its own dedicated question. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The multi-PID result below was **actually observed** from a real `cluster.fork()` setup on Node v24.19.0 — real, distinct process IDs, not a description of load balancing. ##

NODE.JSDECODED.

Easy

How do you run Node.js processes as a background service?

What does NODE_ENV=production actually change and why does it matter?

How do you handle environment variables in Node.js?

Medium

How do you manage configuration in a Node.js application for different environments?

How do you containerize a Node.js app with a small, secure Docker image (multi-stage, distroless)?

How do you implement Server-Sent Events (SSE) in Node.js?

How do you implement rate limiting in a Node.js Express application?

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

What is PM2 and what does it add over running `node server.js` directly?

Explain how clustering works in Node.js.

Hard

When would you use `child_process` module in Node.js?

How do you handle graceful shutdown in a Node.js application?

How does HTTP/2 support work in Node.js and how does it differ from HTTP/1.1?