aws_db_snapshot cost estimation

An aws_db_snapshot is a manual, point-in-time backup of an RDS database instance. Backup storage up to the size of your provisioned database is free; beyond that, snapshots bill per GB-month (~$0.095/GB-month, varying by engine). A 50 GB snapshot is ~$4.75/month.

The nuance is the free allowance: RDS includes backup storage equal to your total provisioned database storage at no charge. Automated backups and manual snapshots draw from that allowance first, so snapshots only start costing money once total backup storage exceeds provisioned DB storage. The cost shows up when you retain many manual snapshots, or keep snapshots of databases you've since deleted (which no longer have a provisioned size to offset them).

The levers: don't accumulate manual snapshots indefinitely (use automated backups with a retention window for routine recovery, and reserve manual snapshots for milestones), and clean up snapshots of deleted instances, which are pure cost with no free allowance behind them.

c3x prices the snapshot from monthly_snapshot_gb at the backup-storage rate; remember the free allowance offsets it up to your DB size.

Terraform example

A minimal but realistic configuration that C3X can estimate.

resource "aws_db_snapshot" "milestone" {
  db_instance_identifier = aws_db_instance.main.identifier
  db_snapshot_identifier = "pre-migration-snapshot"
}

Pricing dimensions

What you actually pay for when you provision aws_db_snapshot.

Dimension	Unit	What's being charged
Backup storage	per GB-month	Snapshot storage beyond the free allowance (free up to total provisioned DB storage). Engine-dependent rate. ~$0.095/GB-month → 50 GB ≈ $4.75/month (above the free allowance)

Sample C3X output

A 50 GB snapshot billed beyond the free allowance:

aws_db_snapshot.milestone
└─ Backup storage   50 GB-month   $4.75
                    Monthly       $4.75

Optimization tips

Common ways to reduce aws_db_snapshot cost without changing the workload.

Use the free backup allowance

Up to the full snapshot cost within allowance

RDS includes free backup storage equal to your provisioned DB size. Automated backups and snapshots within that allowance cost nothing, you only pay above it. Keep total backup storage near or below provisioned DB size to stay free.

Don't accumulate manual snapshots

Per stale snapshot removed

Manual snapshots persist until you delete them and don't expire automatically. Use automated backups with a retention window for routine recovery, and reserve manual snapshots for genuine milestones, then delete them when no longer needed.

Clean up snapshots of deleted databases

Full storage of orphaned snapshots

Once a DB instance is deleted, its snapshots no longer have a provisioned size offsetting them, so they bill in full. Reconcile snapshots against live instances and remove orphans.

Export cold snapshots to S3 for long retention

Backup-storage vs S3 rate

For snapshots you must keep long-term but rarely restore, exporting to S3 (Parquet) can be cheaper than retaining them as RDS backup storage indefinitely.

FAQ

Are RDS snapshots free?

Up to a point. RDS includes free backup storage equal to your total provisioned database storage; automated backups and manual snapshots draw from that first. Beyond it, snapshots bill ~$0.095/GB-month (engine-dependent). A 50 GB snapshot above the allowance is ~$4.75/month.

Why am I paying for snapshots of a deleted database?

Because once the DB instance is gone, there's no provisioned size to offset its snapshots with the free allowance, so they bill in full. Snapshots persist until explicitly deleted, so orphaned snapshots from removed databases are a common cost.

How does c3x estimate the cost?

From monthly_snapshot_gb at the backup-storage rate. Keep in mind the free allowance (up to provisioned DB size) offsets it, the estimate is the storage cost; whether it's billed depends on your total backup vs DB storage.

Related resources

AWS

aws_db_instance

The RDS instance the snapshot backs up; its size sets the free allowance

`aws_db_snapshot` cost estimation