PITR cost on RDS Postgres

Components of Backup Storage Cost

1. Automated Backup Storage:

• Snapshot Storage: This includes the total size of all snapshots (both automated and manual) that are stored. The first snapshot is the full size of the DB instance, and subsequent snapshots store only the changes since the last snapshot (incremental).
• Additional Backup Storage: Beyond the free storage provided for backups (equal to the size of your DB instance), you will be charged per GB per month.

2. Backup Retention:

• Since you have a 10-day retention period, this implies that you will have 10 days’ worth of backup storage. AWS RDS charges are incurred based on the amount of backup storage consumed beyond the free tier (if applicable).

3. Warm Storage:

• Warm storage refers to backup storage for ongoing and recent backups, which is typically more cost-effective than frequent accessing or modifying backup data.

Calculation Details

Given:

• DB Size: 55GB
• Retention Period: 10 days
• Storage Costs:
• Warm Storage Cost: $0.23772 per GB-month
• Backup Storage Cost: $0.118866 per GB-month

Cost Breakdown

1. Automated Backup Storage Cost:

• Total DB Size (55GB) retained for 10 days.
• Cost Calculation: 55 GB×10 days×( 1 month/30 days ) ×$0.23772 per GB-month

Simplifying:

( 55 GB×10 days/30 days )×$0.23772=18.33 GB-months×$0.23772=$4.36

2. Backup Storage Cost:

• Cost Calculation:

55 GB×10 days×( 1 month / 30 days )×$0.118866 per GB-month

Simplifying:

( 55 GB×10 days / 30 days )×$0.118866=18.33 GB-months×$0.118866=$2.18

Total Estimated Cost

Adding the calculated costs for both warm storage and backup storage:

• Warm Storage Cost: $4.36
• Backup Storage Cost: $2.18
• Total Cost: $4.36+$2.18=$6.54

Considerations

• Free Tier: If your total backup storage usage is less than or equal to the size of your DB instance, AWS provides that storage for free. This means the actual cost may be reduced depending on your usage of free backup storage.
• Incremental Backups: Costs are based on incremental changes after the initial full snapshot. If there are significant changes daily, costs may increase due to the increased size of incremental backups.