Glacier-style cold storage
Design a Glacier-style archival cold-storage system optimized for cheapest-possible long-term retention of rarely-read data: think compliance archives and backups, write-once and read-almost-never, eleven-nines durability, and retrieval latency of minutes-to-hours being acceptable. The trick is that storage cost must be a fraction of hot object storage. How do you achieve that cost while keeping data durable and (eventually) retrievable?
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.