Read for behaviour before commenting on style
In a code review interview, first understand the requested behaviour and the patch's effect. Then separate correctness risks from maintainability suggestions and personal preferences. Google's engineering review guidance provides a useful general reference; the exercise and suggested comments below are our own.
This case is for applicants preparing for international engineering teams in Europe. You can complete it without a particular programming language. It tests how you explain review findings rather than whether you remember a vendor's exact interview format.
Review a booking flow with a hidden concurrency risk
The fictional patch checks whether a slot is available, creates a booking, then marks the slot unavailable. Each action happens separately. It returns a success response if the create step completes. The developer has added one test for a successful booking and renamed several variables.
Explain what happens if two requests check availability before either updates the slot. Do not assume separate statements are protected just because they run in one function. Ask what the storage system guarantees and where the invariant of one booking per slot is enforced.
| Finding | Suggested review action |
|---|---|
| Two requests can see availability | Blocking correctness question: how is a second booking prevented? |
| Create succeeds but update fails | Ask about recovery and the resulting booking state. |
| Only happy-path test exists | Request a conflicting-booking and failure-path test. |
| Variable naming preference | Treat as a non-blocking suggestion unless it changes clarity materially. |
Write a comment with a risk and a next step
A useful comment is: 'These operations appear separate. If two requests read an available slot together, could both create bookings? Please show where the one-booking invariant is enforced and add a test for conflicting requests.' It gives the developer a concrete scenario and a verification task.
Avoid prescribing a transaction without understanding the storage design. A database constraint, atomic operation or other coordinated design may be appropriate. Discuss the invariant and failure behaviour first, then evaluate the proposed mechanism. A polite tone does not require weakening a correctness concern.
Follow-up questions to test your reasoning
- What information would make the finding a false alarm?
- What test demonstrates the invariant?
- How would you respond if the author disagrees?
Mark each comment as a required correction, a question or a suggestion. Check whether your strongest finding appears early. If the review is dominated by formatting while the booking risk remains unexplained, rewrite it with the behavioural consequence first.
Practise the discussion after the review
Ask a partner to defend the patch. Explain your concern using the two-request sequence, then listen to the missing context. Change your conclusion if the system already enforces the invariant. Good practice includes discovering that your first interpretation was incomplete.
This is an original Cluegent practice exercise. Its scenario, example wording and suggested timings are illustrative, not an employer's assessment or scoring system. Use genuine experience in a real interview.
For optional preparation, paste the exercise into Cluegent as a typed prompt and ask for one follow-up at a time. Review the reasoning before adopting suggested wording. Redact personal and employer-confidential information. Try Cluegent on Windows or macOS; check the current trial and paid terms before downloading. Follow the employer's rules during an actual assessment.
Browse the Europe interview preparation collection or try Pair programming interview practice: handle a changing requirement.
Sources checked
These official references support the guide. Product details and technical documentation can change; check the linked source for current information.
Where Cluegent helps
Cluegent supports permitted live workflows with transcript context, typed prompts, screenshot-aware answers, resume context, custom response behavior, quick action buttons, and a private desktop overlay. It is most useful when you already understand the subject and need help staying structured under pressure.
Frequently asked questions
What should I check first in a code review interview?
Understand the requirements, changed behaviour and correctness risks before spending time on style preferences.
Should I always suggest a transaction?
No. First identify the invariant and the storage guarantees. Evaluate mechanisms against the actual design and failure modes.