Resumable schema migration
You must migrate 5 years of a 20 TB event history from a legacy schema/storage (old Avro on HDFS, a deprecated partition scheme) to a new lakehouse table with a redesigned schema, WHILE new events keep landing every second and production queries must keep serving the whole time. A single giant batch job has failed twice (OOM, then a transient cluster outage at hour 9) and there's no clean restart point. Design a resumable, verifiable backfill + cutover that tolerates failures and proves the migrated data is correct before you switch reads over.
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.
Clarify5:00 left
Estimate5:00 planned
Design15:00 planned
Deep dive12:00 planned
Failure8:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.