Odoo.sh makes daily backups of the production database. It keeps 7 daily, 4 weekly and 3 monthly backups. Each backup includes the database dump, the filestore (attachments, binary fields), logs and sessions.

Staging and development databases are not backed up. You nevertheless have the possibility to restore a backup of the production database in your staging branches, for testing purposes, or to manually recover data that has been deleted by accident from the production database.

See https://www.odoo.com/documentation/master/administration/odoo_sh/getting_started/branches.html#backups