TypeScript / Node.js Developer track
TypeScript and Node.js interview questions and answers
TypeScript and Node.js interviews test the type system, generics, the event loop and async code. Then you write code. Practice both in one mock interview.
Questions
Interview questions and answers.
Real questions from this track, from easier to harder, with what a good answer covers. In the mock interview, each one comes with follow-ups based on what you say.
What do TypeScript's types give you over plain JavaScript?
A good answer covers that types are checked when you compile, catching mistakes before the code runs.
How do async functions and promises work in Node.js?
A good answer covers that an async function always returns a promise.
How do modules work in TypeScript and Node.js?
A good answer covers that each file is a module that exports what others may import.
How can Node.js handle many requests on one thread?
A good answer covers that Node runs JavaScript on one thread and hands I/O to the system.
What is the difference between an interface and a type alias?
A good answer covers that both can describe the shape of an object.
What is the difference between any and unknown?
A good answer covers that any turns type checking off for that value.
What is a union type, and how do you work with one?
A good answer covers that a union says a value can be one of several types.
How does TypeScript handle null and undefined?
A good answer covers that with strictNullChecks, null and undefined must be part of a type to be allowed.
When and how do you use generics?
A good answer covers that a generic links input and output types, like a function that returns what it was given.
How do you handle errors well in a Node.js service?
A good answer covers that expected errors, like bad input, are returned or thrown as specific error types.
Which tsconfig settings matter most, and why?
A good answer covers that strict turns on the checks that catch the most bugs.
How does TypeScript narrow types, and what is a type guard?
A good answer covers that checks like typeof, instanceof and in narrow a type inside a branch.
What are utility types like Partial, Pick and Record for?
A good answer covers that they build new types from existing ones instead of copying fields.
What are streams in Node.js, and why use them?
A good answer covers that streams process data in chunks instead of loading it all at once.
How do you make sure request data matches your TypeScript types?
A good answer covers that the types say nothing about data arriving at runtime.
Should you use enums in TypeScript?
A good answer covers that enums create real runtime objects while most TypeScript types vanish.
How do you test a TypeScript service?
A good answer covers that unit tests cover logic with a runner like Vitest or Jest.
What are conditional types and mapped types, and when are they worth it?
A good answer covers that a conditional type picks a type based on whether another type matches.
TypeScript types are structural. What does that mean in practice?
A good answer covers that two types with the same shape are compatible, whatever their names.
How do you run many async tasks in Node without overloading a service?
A good answer covers that Promise.all starts everything at once, which can flood a database or API.
How do you find a memory leak in a Node.js service?
A good answer covers that leaks come from things that keep growing, like caches, listeners and timers.
How would you set up a TypeScript monorepo with shared packages?
A good answer covers that a workspace tool links local packages without publishing them.
How do you keep the server and its clients agreeing on API types?
A good answer covers that types copied by hand drift as the API changes.
How would you scale a Node.js API that is running out of CPU?
A good answer covers that a profile shows whether time goes to your code, JSON work or the event loop waiting.
How would you design the types for a TypeScript library many teams use?
A good answer covers that the public types are a contract, so changes follow semantic versioning.
How would you move a large JavaScript codebase to TypeScript?
A good answer covers that allowJs lets JS and TS live together while files move over.
How would you choose between Node.js, Deno and Bun for a new service?
A good answer covers that Node has the widest library support and the most production experience.
What would you measure for a Node.js service in production?
A good answer covers that request rate, errors and latency per route show what users feel.
How would you set TypeScript standards across many teams?
A good answer covers that a shared base tsconfig and lint rules make projects behave the same.
Type checking in a huge TypeScript repo has become very slow. What do you do?
A good answer covers that you find the slow parts with the compiler's trace and diagnostics output.
How would you protect a Node.js codebase from risky npm packages?
A good answer covers that a lock file and clean installs stop versions changing silently.
What are the real benefits and costs of using TypeScript on both client and server?
A good answer covers that shared types and validation code remove a class of mismatch bugs.
What it covers
Topics.
How it works
How the mock interview runs.
Concept questions that start simple and get harder.
Follow-ups on every answer, so you explain the why.
One coding challenge in a live editor.
Your report scores technical correctness, problem-solving & tradeoffs, communication clarity, with quotes from your answers as proof.
Questions.
What TypeScript questions come up most?
Expect type narrowing, generics and union types. You may get any versus unknown. For Node.js, expect the event loop and async code.
How does an Orin mock interview work?
You talk with Orin by voice, like a video call. It asks questions, listens and asks follow-ups based on what you said. Coding happens in a live editor and design on a live whiteboard. After the interview you get a report with quotes from your answers, what cost you points and what to practice next.
Is it free?
Your first interview is free: a 15-minute round with a short coding exercise. No card needed.
Practice the real thing.
A typescript / node.js developer mock interview by voice, with follow-ups and feedback you can use. First interview free.
Start free interview