Scylla Cloud runs a full daily backup to external storage (S3 for AWS, Cloud Storage for GCP). When using your own account (BYOA), backups, like the VMs, are located under the user account. The backup retention time period is 14 days. Scylla Cloud deduplicates SSTables (link) to reduce the storage space and upload time under the hood.
For restoring a backup from a specific day, see Restore a cluster from backup