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# db_instance_automated_backups_replication submodule

> Reference for the db_instance_automated_backups_replication submodule, which replicates RDS automated backups to a second AWS region.

The `db_instance_automated_backups_replication` submodule enables cross-region replication of automated backups for an RDS DB instance. It creates an `aws_db_instance_automated_backups_replication` resource in the **destination** region that continuously replicates backups from the source region.

This is distinct from a cross-region read replica: automated backups replication does not create a live standby instance — it copies backup data to the destination region so that you can restore a DB instance there in a disaster recovery scenario.

## Source

```
./modules/db_instance_automated_backups_replication
```

## Usage

This submodule must be deployed in the **destination** region by configuring an alternate AWS provider:

```hcl main.tf theme={null}
provider "aws" {
  alias  = "primary"
  region = "eu-west-1"
}

provider "aws" {
  alias  = "replica"
  region = "eu-central-1"
}

module "db" {
  source = "terraform-aws-modules/rds/aws"

  providers = {
    aws = aws.primary
  }

  identifier = "my-db"

  engine         = "postgres"
  engine_version = "17"
  # ...

  # Backups are required for replication
  backup_retention_period = 1
}

module "db_automated_backups_replication" {
  source = "terraform-aws-modules/rds/aws//modules/db_instance_automated_backups_replication"

  # Run in the destination region
  providers = {
    aws = aws.replica
  }

  source_db_instance_arn = module.db.db_instance_arn
  kms_key_arn            = aws_kms_key.replica_region.arn
  retention_period       = 14
}
```

<Note>
  The source RDS instance must have `backup_retention_period` set to `1` or greater. Automated backups replication cannot be enabled on an instance with backups disabled.
</Note>

## Input variables

<ParamField path="source_db_instance_arn" type="string">
  The ARN of the source DB instance whose automated backups will be replicated to this region.

  Default: `null`
</ParamField>

<ParamField path="kms_key_arn" type="string">
  The ARN of the KMS encryption key in the **destination** AWS region used to encrypt the replicated backups. If not specified, the default AWS-managed KMS key for RDS is used.

  Default: `null`
</ParamField>

<ParamField path="retention_period" type="number">
  The number of days to retain the replicated automated backups in the destination region. Must be between `1` and `35`.

  Default: `7`
</ParamField>

<ParamField path="pre_signed_url" type="string">
  A pre-signed URL containing a Signature Version 4 signed request for the `StartDBInstanceAutomatedBackupsReplication` action in the source region. Required only when replicating to a region that requires an explicit pre-signed URL.

  Default: `null`
</ParamField>

<ParamField path="create" type="bool">
  Whether to create the automated backups replication resource. Set to `false` to skip creation.

  Default: `true`
</ParamField>

<ParamField path="region" type="string">
  Region where this resource will be managed. Defaults to the region set in the provider configuration.

  Default: `null`
</ParamField>

## Complete example

The `examples/complete-postgres/` and `examples/cross-region-replica-postgres/` examples show this submodule used alongside a KMS module:

```hcl main.tf theme={null}
data "aws_caller_identity" "current" {}

module "kms" {
  source  = "terraform-aws-modules/kms/aws"
  version = "~> 1.0"

  description = "KMS key for cross region automated backups replication"

  aliases                 = ["my-cross-region-rds"]
  aliases_use_name_prefix = true
  key_owners              = [data.aws_caller_identity.current.arn]

  providers = {
    aws = aws.replica_region
  }
}

module "db_automated_backups_replication" {
  source = "terraform-aws-modules/rds/aws//modules/db_instance_automated_backups_replication"

  source_db_instance_arn = module.db.db_instance_arn
  kms_key_arn            = module.kms.key_arn

  providers = {
    aws = aws.replica_region
  }
}
```

## Relationship to cross-region read replicas

| Feature         | Automated Backups Replication         | Cross-Region Read Replica             |
| --------------- | ------------------------------------- | ------------------------------------- |
| What it creates | Backup copies in another region       | A live RDS instance in another region |
| Source          | Any RDS instance with backups enabled | An RDS instance                       |
| Cost            | Storage cost for backup data          | Full instance + storage cost          |
| Restore         | Must manually restore from backup     | Can promote replica to primary        |
| Use case        | Disaster recovery (RPO)               | Read scaling + DR (lower RTO)         |

See the [read replicas guide](/guides/replicas) for documentation on cross-region live replicas.