Backup and restore service
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.
Clarify4:00 left
Estimate4:00 planned
Design11:30 planned
Deep dive9:30 planned
Failure6:00 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.