Question 1

How do you enable gzip/Brotli compression for HTTP responses?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js/Express performance interviews. **Difficulty:** Easy > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The real byte counts below are **actual, measured** raw wire bytes, captured via a client that bypasses automatic decompression specifically to measure what's genuinely sent — not illustrative numbers. ## 1. Why This Even Matters — A Story First Shipping a box stuf

Question 2

Explain how the 'crypto' module secures sensitive data in Node.js

Accepted Answer

**Target Audience:** Engineers preparing for Node.js security-focused interviews — assumes basic hashing/encryption vocabulary. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. Both the successful decryption and the tamper-rejection below were **actually run** on Node v24.19.0 — a real thrown authentication error, not a description of what should happen. ## 1. Why This Even Matters — A Story Fir

Question 3

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 4

What is the purpose of the 'zlib' module in Node.js?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js interviews — assumes basic Buffer/stream familiarity. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The compression numbers below came from **actually running** `zlib.gzipSync`/`gunzipSync` on Node v24.19.0 — real byte counts, not estimated ratios. ## 1. Why This Even Matters — A Story First Vacuum-sealing clothes for storage shrinks them

Question 5

What are some common ways to improve performance in a Node.js application?

Accepted Answer

**Target Audience:** Engineers preparing for Node.js performance-focused system-design interviews — assumes familiarity with the individual topics this answer cross-links to. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The cache timing below was **actually measured** on Node v24.19.0 — a real 104ms-to-0ms difference, not an estimate. ## 1. Why This Even Matters — A Story First A recipe tha

NODE.JSDECODED.

Easy

How do you enable gzip/Brotli compression for HTTP responses?

Medium

Explain how the 'crypto' module secures sensitive data in Node.js

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

What is the purpose of the 'zlib' module in Node.js?

Hard

What are some common ways to improve performance in a Node.js application?