Azure Database for PostgreSQL flexible server: unexpected charges for read replica backups

Question

Greetings, while reviewing the last invoice, we have noticed some unexpected charges related to Azure Database for PostgreSQL flexible server read replicas backups.

According to the Azure Database for PostgreSQL flexible server documentation no backups are taken from read replicas, yet we can see them from both the read replica "Backup Storage Used" metric and billed inside the Subscription billing, even though inside the Backup and Restore section of the read replica we can see "Backups are not supported for read replicas." and no backup is actually listed.

So far we have removed the old read replica and created a new one with a completly new name, but we are still experiencing the same issue.

Both the databases are located in West US 3 and are running PostgreSQL 18.4. We have 1 primary and 1 read replica with the same compute and storage size.

Is this the intended behaviour?

Answer 1

Hi @Enrico De Bon
Thank you for bringing this up.

Based on the Azure Database for PostgreSQL Flexible Server documentation, read replicas do not support independent backups or restore operations. The documentation states that no backups are taken from read replica servers, regardless of their current role. It also notes that if a server previously acted as a primary, any backups created during that period are retained until the configured backup retention period expires.

Reference:

• https://learn.microsoft.com/azure/postgresql/flexible-server/concepts-read-replicas#back-up-and-restore
• https://learn.microsoft.com/azure/postgresql/flexible-server/concepts-backup-restore

If the newly created read replica has never been promoted to a primary, then the backup preservation scenario described in the documentation would not apply. In that case, seeing Backup Storage Used metrics and corresponding backup-related charges associated with the read replica is not explained by the current documentation and would require further investigation.

To better understand the behavior, could you please confirm the following?

• Has either the previous or the newly created replica ever been promoted to a primary server?
• Could you share the billing meter name or the invoice line item associated with the backup-related charges?
• Are the charges specifically attributed to the read replica resource?
• Could you also share screenshots of the Backup Storage Used metric for both the primary server and the read replica?

This information will help determine whether the observed billing behavior is expected or if it requires a deeper review by the product or billing team