Node.js, explained simply
From "what is Node?" to a layered REST API with JWT auth — the event loop, async, Express, middleware, architecture, SQL Server and validation. 103 questions across 11 modules in 4 categories, plus a cheat sheet and flashcards.
How to use this
You're interviewing as a .NET developer who also knows Node. Almost every answer here has a .NET equivalent noted beside it — use that. The goal is to sound comfortable, not to sound like a Node specialist. Module 07 (the event loop) is the one they will definitely ask about.
| If you have… | Do this |
|---|---|
| 1 day | All 11 modules in order. |
| 4 hours | Modules 01, 05 (Express), 06 (async), 07 (event loop), 08 (middleware), 10 (JWT). |
| 2 hours | Module 07 in full, then Module 06 Q56 and Q59, then Module 08 and Module 10. |
| 30 minutes | Cheat sheet, then the five predict the output boxes. |
The four questions that decide it
| Question | Where |
|---|---|
| "What's the output?" — promise vs setTimeout vs nextTick | Module 07, Q65 |
| "Does await block the server?" — no, and here's what does | Module 06, Q59 & Module 07, Q70 |
| "Is Node single-threaded?" — your JavaScript is; the process isn't | Module 07, Q66 |
| "How would you structure an API?" — route → controller → service → repository | Module 09, Q81–Q82 |
Being able to describe blocking the event loop — what it looks like in production (latency rising on every endpoint at once, one core at 100%), what causes it, and how you'd measure it with an event-loop lag metric. Hardly anyone volunteers that, and it's the clearest sign you've actually run Node rather than read about it. Module 07, Q70.
The sidebar search covers all 103 questions from any page — try "event loop", "middleware", "promise", "JWT", "req.body", "package.json", "validation". Results link straight to the answer.