Which type of AWS storage enables optional server-side encryption using KMS?

The correct answer indicates that all the mentioned AWS storage types, Amazon S3, AWS EFS, and AWS RDS, support optional server-side encryption using AWS Key Management Service (KMS).

Amazon S3 allows users to store and retrieve any amount of data at any time, with the option to encrypt data server-side using KMS. This means that while the data is stored, it can be automatically encrypted and decrypted without needing to manage encryption keys personally.

For AWS Elastic File System (EFS), server-side encryption can also be enabled, allowing users to be assured that data is protected while at rest by leveraging KMS for encryption key management, ensuring compliance and security requirements are met.

Similarly, AWS Relational Database Service (RDS) supports encryption at rest by enabling server-side encryption using KMS keys. This ensures that the databases contain sensitive information can remain secure.

By recognizing that all these storage solutions offer the capability of server-side encryption with KMS, it highlights AWS's commitment to data security across different services, conforming to best practices for data protection. The availability of encryption options in each of these services makes it easier for users to manage sensitive information securely while also meeting various regulatory requirements.