Code RoomSchema cache skew silent corruption
HardPrep Room Coding #2497

Schema cache skew silent corruption

On-callReliability & on-callSenior–Staff~40 min

Analysts report that a downstream table's `amount_cents` values look 'shifted' — many rows have plausible-but-wrong numbers, and a few fields are swapped with adjacent ones. No errors anywhere: ingestion succeeds, the consumer commits, dashboards are green. Context: 90 minutes ago a producer team deployed a change that added a new field in the MIDDLE of an Avro record's field list and bumped the schema, but a subset of consumers are pinned to an older Schema Registry cache and didn't pick up the new schema. How do you triage this silent corruption, stop it spreading, and recover the affected rows?

What a strong answer looks like

Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.

0:00 of about 40 min
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.