Ghosts of Snapshots Past

A easy ai_coding interview practice problem on DataDriven. Write and execute real ai_coding code with instant grading.

Domain

ai_coding

Difficulty

easy

Seniority

L4

Problem

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.

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