Prepare for an FDE debugging interview exercise

Debugging interviews test reasoning under incomplete evidence. Narrate a disciplined path rather than guessing at a fix.

Order the investigation

The delivery lab uses a duplicate-order fixture.

from delivery_cases import debugging_interview_case

result = debugging_interview_case()
assert result["jumps_to_fix"] is False
assert result["evidence_before_repair"] is True
assert result["steps"][0] == "clarify expected idempotency"
assert "timeout" in result["prompt"]["logs"][0]

Clarify expected/actual behaviour, scope and constraints. Reproduce with minimal safe input. Use logs, stack, request IDs and code path to rank hypotheses. Change one variable, add a failing regression and repair the violated contract. Verify neighbouring and failure cases.

Communicate uncertainty and ask for missing evidence. Avoid production access assumptions, broad rewrites and blaming users. Close with root cause, fix, trade-off and prevention.

The FDE for Freshers course covers technical screens, take-homes and demo defence.

Exercise

Give a peer the fixture without the cause. Score hypothesis quality, evidence use, test-before-fix and communication; switch roles and repeat.

Continue learning

This article is part of the FDE career entry and client-delivery practice sequence. Use the neighbouring tasks when you need the prerequisite or the next application.

• Review the prerequisite or neighbouring task in Build a portfolio around evidence rather than screenshots.
• Continue with Practice a difficult-client roleplay with a scoring rubric.

Reference: GOV.UK QA guidance.