Code comprehension interview practice
Not every coding interview starts from a blank editor. In a code comprehension round you're handed code you've never seen and asked to explain it, trace it, find what's broken and fix it without breaking anything else. It's much closer to day-to-day engineering than an algorithm puzzle.
PrepLinx loads an unfamiliar starter codebase with planted defects into your editor. The AI interviewer asks you to summarize it, trace specific inputs through it and diagnose the bugs, and never confirms whether you've found them. You fix them in the editor and explain what your fix could break.
What this round tests
Comprehension
Summarizing what the code does and how its parts relate.
Tracing
Walking an input through the execution path accurately.
Bug diagnosis
Finding the defects and explaining where they are.
Root cause
Explaining why each bug happens, not just where.
The fix
Changes that fit the existing structure and style.
Regression awareness
Saying what your fix could break and how you'd test it.
Practice questions
Examples of the questions and follow-ups you can expect. Practice saying your answers out loud, not just reading them.
- Summarize what this codebase does and how the files relate to each other.
- Trace what happens when this function receives an empty list.
- One of the tests fails. Where's the defect, and why does it happen?
- Fix it. What else could your change break?
- Extend this to support a new requirement without changing its public interface.
- How would you test that your fix works?
How a PrepLinx session works
- 1
Choose the round
Pick the role, the interview type and a difficulty (easy, medium or hard). Optionally add a job profile with your resume and the job description, so the questions relate to that job.
- 2
Interview out loud
The AI interviewer speaks, listens to your answers and asks follow-ups. It doesn't give hints or say whether you're right, just like the real thing. The session runs up to 60 minutes.
- 3
Get scored feedback
A report with a 0–10 score for each dimension the round is graded on, strengths quoted from your own words, weaknesses, concrete improvements and an overall hiring signal, plus the full transcript.
How to prepare
Read before you touch
Find the entry points and main data structures first, then the details. Changing code before you understand it is an easy way to add new bugs.
Narrate as you read
Your thinking aloud is what's being graded. Say what you think each part does, even when you're unsure.
Look for broken assumptions
Bugs often sit where an assumption fails: an off-by-one, a missing null check, shared state.
Fix the cause, not the symptom
Explain why the bug happens before you change anything, then fix it at the source.
Respect the existing style
Match the code's conventions. Interviewers notice when a fix rewrites more than it needs to.
Frequently asked questions
What is a code comprehension interview?
A round where you read, explain, debug and extend existing code instead of writing a solution from scratch. It tests skills you use every day at work: understanding unfamiliar code and changing it safely.
Does the interviewer tell me when I've found a bug?
No. As in a real round, it neither confirms nor denies. The feedback report at the end scores your diagnosis, your root-cause reasoning and your fixes.
Is it the same as a code review interview?
They're closely related: both test reading unfamiliar code critically. Code comprehension also asks you to trace execution and implement the fixes, so practicing it prepares you for code review rounds as well.
How long is a session?
Up to 60 minutes.
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Practice your next code comprehension interview
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