Ghosts of Snapshots Past
An easy AI Coding mock interview question on DataDriven, with an AI interviewer who asks follow-up questions and a hire or no-hire decision at the end.
- Domain
- AI Coding
- Difficulty
- easy
- Seniority
- L4
Interview Prompt
Yesterday a bad backfill wrote 2M corrupt rows into events_iceberg. We rolled back to the prior snapshot. Now an analyst's AS OF (timestamp) query for a window two days before the rollback is also returning the corrupt rows. Reproduce by running tests/test_time_travel.py. The bug is in how our reader resolves a snapshot for a timestamp; fix it so AS OF queries reflect what was visible at that time.
Summary
The past keeps rewriting itself.
How This Interview Works
- Read the task and the repository: the files, the failing check and the constraints
- Work the fix with the AI agent at your side, and run the checks until they pass
- Submit, then answer the interviewer's questions about the change you made
- Get a hire or no-hire decision with feedback on how you drove the agent