$1000 charge for Azure Database for PostgreSQL Flexible Server Backup Storage

Question

I recently ran a restore for a client and received a charge on my latest bill for nearly $1,000. I am trying to figure out why the charge was so large considering the brief backup time and the server was deleted.

Answer 1

Hello @Steve Willis@Steve Willis Thank you for posting your query on Microsoft Q&A forum.

The charge is expected behavior based on how Azure Database for PostgreSQL – Flexible Server bills backup storage, especially when restores (PITR) and geo‑redundant backups are involved.

1. Backup storage is billed separately from compute:

Azure PostgreSQL Flexible Server includes free backup storage equal to 100% of the provisioned server storage. Any backup storage beyond that limit is billed per GB per month, regardless of how long the server existed.

Example If the server had 512 GiB of provisioned storage:

• First 512 GiB of backups → free
• Any additional snapshot + WAL data → billable

2. Restore operations can significantly increase backup storage usage.

When you perform a Point‑in‑Time Restore (PITR):

• Azure must retain all snapshots and WAL logs needed to support recovery within the configured retention window
• The restored server inherits the same backup retention and redundancy settings as the source
• During the time both the original and restored servers exist, total backup storage can temporarily spike

3. Geo‑redundant backup doubles effective storage consumption.

If the source server was configured with geo‑redundant backup storage:

• Backups are stored in the primary region and replicated to the paired region
• Backup billing effectively accounts for two copies of the data

This can cause backup charges to rise quickly, even for short‑lived servers.

4. Backup retention applies even if the server is deleted.

Deleting a PostgreSQL Flexible Server does not immediately eliminate backup storage charges already incurred:

• Backups are retained according to the configured 7–35 day retention period
• Charges reflect actual GB‑days stored, not just server lifetime

So even if the server existed briefly, the backup data generated during restore remains billable until it ages out.

The ~$1,000 charge is typically driven by a combination of:

• Large data size and/or high WAL generation
• PITR restore temporarily duplicating backup data
• Geo‑redundant backup storage
• Backup retention applying after deletion

References:

• Backup and restore concepts – Azure Database for PostgreSQL https://learn.microsoft.com/azure/postgresql/backup-restore/concepts-backup-restore [learn.microsoft.com]
• Restore PostgreSQL Flexible Server (Geo‑redundancy and charges) https://learn.microsoft.com/azure/backup/tutorial-restore-postgresql-flex [learn.microsoft.com]

Thanks,

Suchitra.

Answer 2

The large charge is due to how Azure bills backup storage for Azure Database for PostgreSQL flexible server, especially when restores are performed and when backup data size and redundancy are high.

Key points that explain the ~$1,000 charge:

1. Backup storage is billed separately from compute
   • Azure Database for PostgreSQL flexible server includes free backup storage up to 100% of the provisioned server storage. Any backup storage beyond that is billed in GB/month.
   • Example from the service: if the server has 250 GiB of provisioned storage, 250 GiB of backup storage is free; anything above 250 GiB is charged.
   • Heavy transactional activity (many WAL files) increases backup size and therefore cost, regardless of how briefly the server was in use.
2. Geo-redundant backup doubles effective backup size
   • If the server was configured with geo-redundant backup, backups are stored in the primary region and copied to the paired region.
   • Billing formula in that case is:

     (2 × local backup size − provisioned storage size) × price per GB/month

   • This can significantly increase costs if backup size is large relative to provisioned storage.
3. Backup retention window drives how much data is stored
   • Backup retention can be set between 7 and 35 days.
   • All backups and WAL logs required to support point-in-time recovery (PITR) within that window are retained.
   • Even if the server existed only briefly, if there was intensive activity and a longer retention period, the accumulated backup data can be large and billable.
4. Restores and PITR do not reset or eliminate backup charges
   • Performing a point-in-time restore (PITR) creates a new server with the same backup retention and redundancy configuration as the source.
   • The original server’s backups remain in backup storage until they age out of the retention window or the server is deleted and its backup-retention rules are applied.
   • During the period when both original and restored servers exist (and generate backups/WAL), total backup storage can spike.
5. Deleting the server does not immediately remove backup charges already incurred
   • For active servers, backups are retained according to the configured retention period. Charges apply for the backup data stored during that time.
   • For stopped servers, no new backups are taken, but existing backups within the retention window are still stored and billed.
   • For deleted flexible servers, backups are retained for a short period (for dropped-server recovery) and then removed; however, backup storage that existed before deletion has already contributed to the billing period.
6. Additional Azure Backup (vaulted backup) charges if Azure Backup was used
   • If Azure Backup was configured for the PostgreSQL flexible server (vaulted backups), there are two cost components:
     • Protected instance fee based on database size (per 250 GB unit).
     • Backup storage fee for data stored in the Backup Vault (vault-standard tier), based on GB and redundancy.
   • These are in addition to the built-in service backup storage behavior and can significantly increase the bill if large or frequent restore points were created.
7. How to verify the source of the charge
   • In the Azure portal, check the Backup Storage Used metric on the PostgreSQL flexible server to see how much backup data was stored during the billing period.
   • Review:
     • Provisioned storage size.
     • Backup retention period.
     • Backup redundancy (locally redundant vs geo-redundant).
     • Whether Azure Backup (vaulted backups) was enabled for the server.
   • Compare these with the pricing model for Azure Database for PostgreSQL flexible server and, if applicable, Azure Backup for PostgreSQL flexible servers.
8. What to do next
   • Reduce future costs by:
     • Lowering backup retention (if compliant with requirements).
     • Using locally redundant instead of geo-redundant backup where acceptable (must be chosen at server creation).
     • Monitoring Backup Storage Used regularly.
   • For the existing $1,000 charge, open a billing support request in the Azure portal so a billing engineer can break down the exact backup and vault usage that produced the charge.

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References:

• Backup and restore in Azure Database for PostgreSQL
• About Azure Database for PostgreSQL - Flexible Server backup
• What is Azure Database for PostgreSQL backup?
• Restore a dropped Azure Database for PostgreSQL