Software Engineer mock interview questions
Software engineering interviews mix coding and system design with behavioural rounds. The behavioural round is often where strong engineers lose offers, because they have never practised telling their work as a story.
What interviewers look for
- Problem solving
- Clarifying the problem before writing code.
- Technical depth
- Trade-offs you can explain, not only solutions.
- Communication
- Thinking out loud so the interviewer can follow.
- Ownership
- Bugs, incidents and decisions you took responsibility for.
The questions to practise
Grouped by type. The note beside each says what the interviewer is really testing, which is what your answer has to show.
Behavioural
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Tell me about the hardest bug you have fixed.
- What it tests
- Debugging method and persistence.
-
Describe a technical decision you would make differently now.
- What it tests
- Reflection and growth.
-
Tell me about a time you disagreed with a code review.
- What it tests
- Collaboration and standards.
-
Describe a production incident you were involved in.
- What it tests
- Ownership under pressure.
Technical and design
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How would you design a URL shortener?
- What it tests
- System design basics: storage, scale, trade-offs.
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Explain the difference between a process and a thread.
- What it tests
- Fundamentals, explained simply.
-
How do you decide when code is ready to ship?
- What it tests
- Testing and quality judgement.
-
Walk me through how you would find a memory leak.
- What it tests
- Structured debugging.
-
How would you make a slow API endpoint faster?
- What it tests
- Measurement before optimisation.
Situational
For the questions every interview asks, whatever the role, see the full list of mock interview questions.
An example answer, told with STAR
Situation, task, action, result. The structure is what to copy; the story should be yours.
“Tell me about the hardest bug you have fixed.”
- SSituation
Checkout requests were failing for about 2% of users, only in production.
- TTask
Find the cause quickly without being able to reproduce it locally.
- AAction
I added request tracing, spotted that every failure came through one load balancer, and traced it to a stale TLS certificate on that node.
- RResult
We fixed it within the day, and I added certificate-expiry alerts so it could not happen silently again.
Mistakes to avoid
- Starting to code before clarifying requirements and edge cases
- Going silent while thinking, so the interviewer cannot follow
- Behavioural answers that describe the technology but not your decisions
Practise it in Huru
Choose what to practise
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Answer on camera
Huru asks the questions and records your answers, so you rehearse saying them, not reading them.
Fix one thing and go again
Every answer is scored out of 100, with what worked, the one thing to fix and a stronger version.
Software Engineer interview: questions
What questions are asked in a software engineer interview?
How do I practise the behavioural round for software engineering?
Go deeper on the Huru blog
Mock interview questions for other roles
Practise your software engineer interview out loud
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