Which AWS feature ensures data remains encrypted during replication between S3 buckets?

The feature that ensures data remains encrypted during replication between S3 buckets is S3 Encryption with KMS (Key Management Service). When you enable server-side encryption with KMS keys for your S3 objects, the data is encrypted before being replicated, securing it both at rest and during transmission. This means that even as the data is copied to another bucket, the encryption is maintained, providing additional security and compliance for sensitive information.

Using KMS allows for more granular control over encryption keys, including the ability to manage permissions related to who can use those keys, ensuring that only authorized users have access to the data.

The other options do not directly address data encryption during replication. Access Control Lists (ACL) manage permissions for accessing S3 objects but do not provide encryption. Versioning protects against data loss and enables object recovery but does not inherently encrypt data. Object Lock is designed for data retention policies and immutability rather than encryption during replication. Thus, S3 Encryption with KMS is the correct feature for ensuring that data remains encrypted during the replication process between S3 buckets.