Excessive RDS Backup Retention

CloudZero has identified Amazon RDS backups and manual snapshots retained beyond 90 days, potentially exceeding business or compliance requirements. Long-term retention of RDS snapshots accumulates significant costs over time.

What it does

This recommendation identifies RDS backups and snapshots that are:

• Older than 90 days
• Incurring ongoing storage costs
• Potentially exceeding necessary retention requirements

RDS automated backups retain for 7-35 days and auto-cleanup. This focuses on manual snapshots retained indefinitely unless explicitly deleted.

Why it matters

• Cost Accumulation: Storage costs add up as snapshots accumulate ($0.095/GB-month)
• Forgotten Snapshots: Manual snapshots for one-time purposes often get forgotten
• Example: 50 old 500GB snapshots = ~$28,500/year in unnecessary costs

Recommended Actions

1. Review Snapshot Inventory:

   • Navigate to RDS → Snapshots → Filter "Manual snapshots" → Sort by date
   • Identify purpose of each snapshot (testing, compliance, migration, etc.)
   • Determine which are still needed
   Bash

   aws rds describe-db-snapshots --snapshot-type manual \
     --query 'DBSnapshots[?SnapshotCreateTime<=`2023-01-01`].[DBSnapshotIdentifier,SnapshotCreateTime]'

2. Establish Retention Policy:

   • Daily backups: 7-30 days
   • Weekly backups: 4-12 weeks
   • Monthly backups: 12 months
   • Yearly backups: 7 years (compliance only)
   • Document and communicate policy

3. Delete Unnecessary Snapshots:

   Important: Deletion is permanent - always verify first

   Bash

   aws rds delete-db-snapshot --db-snapshot-identifier mydb-snapshot-2023-01-15

4. Implement Automated Lifecycle:

   • Use AWS Lambda to auto-delete based on tags and age
   • Tag snapshots: Purpose, RetentionDays, Retain
   • Use AWS Backup for centralized lifecycle management

5. Consider Alternative Storage:

   • Export to S3 Glacier Deep Archive (~$0.00099/GB-month, 99% cheaper)
   • Use AWS Backup archive tier
   • Keep only "hot" backups in RDS format

6. Monitor and Alert:

   • Set up Cost Anomaly Detection for RDS backup storage
   • Create CloudWatch dashboards for snapshot age and costs
   • Alert on snapshots exceeding retention policy

Cost Impact

• Conservative estimate: 50% reduction (assumes some retention needed)
• Unnecessary snapshots: 100% recoverable
• Pricing: ~$0.095/GB-month (standard), ~$0.021/GB-month (Aurora excess)

Important Considerations

Retention Best Practices

Keep:

• Compliance-required snapshots
• Recent backups (30-90 days) for disaster recovery
• Pre-migration/upgrade snapshots (until validated)

Consider Deleting:

• Ad-hoc test snapshots
• Post-deployment snapshots (after validation)
• Duplicate snapshots
• Decommissioned database snapshots

Operational Risks

• Deletion is permanent (no undelete)
• Verify with database owners before deletion
• Export to S3 if uncertain
• Test that remaining snapshots are restorable

AWS Backup Alternative

Use AWS Backup for automated lifecycle management:

• Centralized management across services
• Automated retention and expiration
• Compliance reporting
• Cold storage transitions