Engineering

Software Engineer mock interview

At this level the loop is calibrated for potential rather than track record: expect clean fundamentals, a coding round you narrate out loud, and behavioral questions about collaboration rather than leadership.

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

Software 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. Walk me through a project you built end to end. What did you own?
  2. Tell me about a bug that took you far too long to find.
  3. How would you store and look up ten million key-value pairs?
  4. When have you disagreed with a code review comment?
  5. What would you change about the last codebase you worked in?
  6. How do you decide when a piece of code is done?

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.

Tell me about a bug that took you far too long to find.

What loses marks

Naming the bug and the fix. "There was a null pointer, I added a check." It answers the question and demonstrates nothing.

What scores

The hunt, in order: what you saw, what you assumed, the thing that disproved the assumption, and what you changed afterwards so it could not happen silently again. The debugging process is what is being assessed, not the defect.

Why Software Engineer candidates get cut

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

Silent coding. Working out the answer without narrating is scored as if you had no reasoning at all — the interviewer cannot mark what they cannot hear.
Jumping to code before restating the problem or asking about constraints, then solving a different question from the one asked.
Behavioural answers with no 'I' in them. At this level interviewers are calibrating for potential, and a candidate who only says 'we' gives them nothing to calibrate.

Start with a general round

For Software 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 Software 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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