Blob store with deduplication
Design a blob store with global deduplication for a backup/sync product (think Dropbox-style file storage). Constraints: petabytes stored, high duplication across users (same OS images, shared documents), block-level dedup with variable-size content-defined chunking, 10 nines durability, and you must never lose a block that is still referenced. Cover chunking, the dedup index, and reference lifecycle.
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.
Clarify4:30 left
Estimate4:30 planned
Design13:30 planned
Deep dive10:30 planned
Failure7:00 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.