Azure backups occur every few minutes as per the documentation for Automated backups:
SQL Database supports self-service for point-in-time restore (PITR) by automatically creating full backup, differential backups, and transaction log backups. Full database backups are created weekly, differential database backups are generally created every 12 hours, and transaction log backups are generally created every 5 - 10 minutes, with the frequency based on the compute size and amount of database activity.
When do index rebuilds occur in Azure SQL? Are they automatic or manually selected in a maintenance window?