Every question below is one that gets asked. What we have added is the part that usually goes unsaid: what a strong answer actually demonstrates. Career1 scores interviews for a living, so this is the difference we see between an answer that lands and one that was rehearsed.
The event loop and async
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What happens when you block the event loop, and how would you notice?
What a strong answer shows: The difference between reading about it and living it. Strong answers mention latency climbing across every request, not just the slow one.
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Explain the difference between process.nextTick and setImmediate.
What a strong answer shows: Precision. Almost everyone knows the phases exist; fewer can say which runs first and why that ever mattered to them.
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You have 500 records to process through an async API. How do you do it?
What a strong answer shows: Whether you reach for Promise.all on all 500 and take down the downstream service, or talk about batching and concurrency limits.
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How do you handle an unhandled promise rejection in production?
What a strong answer shows: That you know it can terminate the process, and that logging it and moving on is not a strategy.
Streams, memory and performance
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When would you use a stream instead of reading a whole file?
What a strong answer shows: Understanding of memory pressure. The best answers come with a story about a file that got bigger than anyone planned for.
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A Node service leaks memory over a few days. How do you find it?
What a strong answer shows: Method: heap snapshots, comparing over time, and the usual suspects like closures over request scope and unbounded caches.
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How would you scale a Node service across CPU cores?
What a strong answer shows: Whether you know a single process uses one core, and can talk about cluster, worker threads or just running more containers.
Working in a real codebase
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How do you decide between CommonJS and ES modules on a new service?
What a strong answer shows: Awareness of tooling reality rather than fashion, including what breaks in your test runner.
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What does your error handling look like across an Express or Fastify app?
What a strong answer shows: Whether errors are handled in one place or scattered, and whether the client gets something useful.
Now practise it out loud
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Practise this interview freeQuestions people ask
What Node.js topics come up most in interviews?
The event loop, async patterns and their failure modes, streams, and how you debugged something slow in production. Framework specifics come up far less than candidates expect, because teams assume you can learn their framework.
How technical are Node interviews, really?
Usually one conversation about your experience, one live or take-home coding exercise, and one system design or debugging discussion. The debugging conversation is where most candidates separate, because it cannot be crammed.
Should I mention TypeScript in a Node interview?
Yes, if you have used it. Most teams hiring Node developers now write TypeScript, and how you talk about typing an existing JavaScript codebase is a useful signal in itself.
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