System designHardsd-g718

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

Question

Design a deduplicating backup-and-restore system for an enterprise fleet: thousands of machines back up nightly, most data is unchanged or duplicated across machines (OS files, shared assets), and you need space-efficient storage, fast incremental backups, and reliable point-in-time restore of any machine. How do you deduplicate, store, and restore — and what breaks at scale?

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.