Amazon S3 Cross-Region Replication (CRR) is a feature that automatically replicates objects from an S3 bucket in one AWS Region to another S3 bucket located in a different Region.
It is mainly useful when organizations need better disaster recovery, business continuity, compliance, or geographically distributed data access.
How S3 CRR Works
With CRR, you configure a source S3 bucket and a destination bucket in another AWS Region. When eligible objects are added or updated in the source bucket, S3 can replicate them to the destination based on the configured replication rules.
For example:
S3 Bucket — Mumbai → S3 Bucket — Singapore
If an important file is stored in the Mumbai bucket, a replicated copy can be maintained in the Singapore bucket.
Important Requirements
Before configuring CRR, you generally need to:
- Enable versioning on both source and destination buckets.
- Configure appropriate IAM permissions for replication.
- Define which objects should be replicated using replication rules.
- Configure encryption and permissions correctly if the objects use server-side encryption.
- Consider replication of delete markers and other supported object metadata based on your requirements.
Why Use CRR?
CRR can provide an additional copy of data outside the primary AWS Region, which can be valuable if a regional issue affects access to the source data. It can also help organizations serve users in different geographical locations or meet certain data-residency and compliance requirements.
One important point is that CRR is replication, not a complete backup strategy. Organizations should still consider retention, versioning, recovery procedures, and other backup requirements.
In simple terms, S3 CRR keeps copies of selected S3 objects synchronized across different AWS Regions, helping improve resilience and availability for important data.