System designHardsd-g717

Subject Cold storageLevel Senior–Staff~45 minCommon in Storage & CDN interviewsIndustries Technology

Question

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.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.