Question 1

What does the Node.js --watch flag do and how does it replace nodemon?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js developer-tooling interviews. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The restart-with-a-new-PID below was **actually observed** from a real running `node --watch` process after a real file edit — not a description of documented behavior. ## 1. Why This Even Matters — A Story First Manually killing a terminal process and re-typing the

Question 2

What is the difference between readFile and createReadStream in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — assumes very basic `fs` module familiarity. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The numbers below came from **actually reading a real 20MB file** both ways on Node v24.19.0, not a description of expected behavior. ## 1. Why This Even Matters — A Story First Moving a house's contents in one giant crate needs a crane

Question 3

What is the role of the path module and why is it preferred over manual string concatenation?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — no prior file-system path handling experience assumed. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every path shown below was **actually produced** by running the code on Node v24.19.0 (on Windows, for this run), not written by hand as an illustration. ## 1. Why This Even Matters — A Story First Writing an address by hand,

Question 4

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 5

What are the main security risks of using the 'eval()' function in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js security-focused phone screens — no prior security background assumed. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every consequence below was **actually demonstrated by running real code**, not described as a hypothetical. ## 1. Why This Even Matters — A Story First Handing a stranger a blank check with your signature already on it is fun

Question 6

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 7

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 8

What is the difference between blocking and non-blocking I/O in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js interviews — assumes basic `fs` module and event-loop familiarity. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The tick counts and timings below came from **actually running both versions** on Node v24.19.0 against a real 50MB file, not a description of expected behavior. ## 1. Why This Even Matters — A Story First A single toll-booth work

Question 9

What is the use of the 'os' module in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — no prior systems-programming background assumed. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Every value below was **read directly from this real machine**, not written as a generic placeholder example. ## 1. Why This Even Matters — A Story First A moving crew arriving at an unfamiliar building first checks a few basic fact

Question 10

What is the role of the V8 JavaScript engine in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js phone screens — no prior engine-internals knowledge assumed. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The version number below was read directly from a running Node process, not quoted from memory. ## 1. Why This Even Matters — A Story First A car's engine and its dashboard, seatbelts, and cargo hold are built by different teams for dif

NODE.JSDECODED.

Easy

What does the Node.js --watch flag do and how does it replace nodemon?

What is the difference between readFile and createReadStream in Node.js?

What is the role of the path module and why is it preferred over manual string concatenation?

Explain how modules work in Node.js.

What are the main security risks of using the 'eval()' function in Node.js?

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

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

What is the difference between blocking and non-blocking I/O in Node.js?

Medium

How does the Node.js event loop work?

How would you implement caching in a Node.js application?

Explain the concept of 'event-driven architecture' in Node.js.

What are 'Event Emitting' patterns and how does error-first callback convention relate to them?

When would you choose Node.js over other backend technologies?

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

How do you implement a custom Transform stream?

What are Worker Threads in Node.js and when would you use them?

Hard

What is `process.nextTick()` and `setImmediate()` and when to use them?

How do you profile CPU usage with --prof, 0x, or clinic.js flame graphs?

Explain how memory management and Garbage Collection work in the V8 engine.

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

What are memory leaks in Node.js and how do you detect them?

What is backpressure in Node.js streams and how do you handle it?

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

How do you implement microservices communication in Node.js?