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.