Engineering

Full-Stack Engineer mock interview

The risk here is being assessed as shallow on both sides. Pick a depth to demonstrate — usually the backend — and be explicit about where your expertise thins out rather than bluffing across the whole stack.

Engineering loops are the most structured of any discipline, and the most predictable. Expect a recruiter screen, one or two technical rounds, a system design conversation at mid-level and above, and a behavioral round that is usually underestimated.

The technical rounds are rarely won on the answer. They are won on narration — whether the interviewer can follow your reasoning while you work, and whether you say the trade-off out loud instead of silently picking one.

The rounds you can practise

Each round is run by the interviewer built for it, with its own scoring axes — not one generic interviewer asked to change subject.

System design, trade-offs, and war stories from production.

Scored on Technical communication · Engineering depth · Ownership & collaboration

System design, trade-offs, and war stories from production.

Scored on Technical communication · Engineering depth · Ownership & collaboration

Hands-on problem solving, code quality, debugging, and engineering judgment.

Scored on Problem-solving communication · Engineering correctness · Adaptability & craft

System design, trade-offs, and war stories from production.

Scored on Technical communication · Engineering depth · Ownership & collaboration

Technical Deep-Dive

Theo · Principal Engineer

Hands-on problem solving, code quality, debugging, and engineering judgment.

Scored on Problem-solving communication · Engineering correctness · Adaptability & craft

Full-Stack Engineer interview questions

Six you can expect, in the register interviewers actually use. Answer them out loud before you read the next section — reading a question and answering one are different skills, and only the second is marked.

  1. Which half are you stronger in, and what does the weaker half cost you?
  2. Walk me through a feature end to end — schema to pixels.
  3. Where do you put business logic, and why not the other side?
  4. How do you decide an API shape when you are also writing the client?
  5. Tell me about a time the frontend and backend assumptions diverged.
  6. How do you keep types honest across the boundary?

The same question, answered badly and well

The gap between these two is most of your score, and it is easier to see than to be told.

Which half are you stronger in, and what does the weaker half cost you?

What loses marks

"I'm comfortable across the whole stack." Interviewers hear this constantly and read it as a candidate who is mid at both and cannot self-assess.

What scores

Pick one, name it, and be concrete about the gap — 'backend; I can build the interface but I would not be the person choosing the state management approach for a large app, and here is what I do about that.' Calibrated self-assessment scores; breadth claims do not.

Why Full-Stack Engineer candidates get cut

The post-mortem nobody sends you. These are specific to this loop rather than general interview advice.

Bluffing depth on both sides, which collapses the moment one pointed question lands.
Describing the feature as a sequence of tasks rather than a set of decisions with an owner.
No opinion on where logic belongs, which suggests you have never been on the wrong side of that choice.

Start with a general round

For Full-Stack Engineer, a general round runs with Kai system design, trade-offs, and war stories from production. It is the fastest way to find out which round you actually need to work on. The first session is free.

Practise a Full-Stack Engineer interview →

Question guides

Before you practise, it is worth reading how the common rounds are marked: tell me about yourself, behavioral questions and STAR, and system design.

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