A company wants to move its application to a serverless solution. The serverless solution needs to analyze existing data and new data by using SQL. The company stores the data in an Amazon S3…

AWS KMS multi-Region keys allow you to encrypt data in one AWS Region and decrypt it in another using the same logical key, which is crucial for cross-Region replication. This significantly reduces the operational overhead associated with managing separate KMS keys or sharing key material across Regions, ensuring consistent encryption and decryption for data that needs to be replicated and accessed in different AWS Regions, thus simplifying the management of encrypted replicated data.

Server-side encryption with Amazon S3 managed keys (SSE-S3) does not provide the same level of key management control as KMS, nor does it inherently simplify decryption of replicated data across regions, as it relies on AWS managing keys per region.

While configuring Cross-Region Replication (CRR) on an existing S3 bucket with SSE-S3 handles both replication and encryption, SSE-S3 keys are managed by AWS on a per-region basis, which doesn't offer the unified key management for decryption across regions that multi-Region KMS keys provide, potentially leading to more operational overhead if specific key consistency is required.

Configuring CRR with SSE-KMS using standard KMS keys requires careful management of key access or replication to allow decryption in the destination region. Standard KMS keys are regional, making it complex to decrypt data encrypted by one key in a different region without extra setup, which increases operational overhead compared to multi-Region keys.