System designMediumsd-g602

Subject Backup restore storageLevel Mid–Senior~35 minCommon in Storage & CDN interviewsIndustries Technology, IT services

Question

Design a backup-and-restore service for enterprise customers backing up databases and VM disk images. Constraints: nightly full + frequent incrementals, point-in-time restore to any of the last 35 days, RPO of 1 hour and RTO of under 4 hours for a multi-TB dataset, immutable/ransomware-resistant backups, and storage cost must stay bounded as retention grows. Cover the backup chain, dedup, and restore.

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.