Which AWS storage service should be used?

Explanations:

Amazon EBS (Elastic Block Store) is designed for use with a single EC2 instance and does not support concurrent access from multiple instances, making it unsuitable for scenarios where multiple EC2 instances need simultaneous access to a shared file system.

Amazon EFS (Elastic File System) is specifically designed to provide a shared file system for multiple EC2 instances, allowing for concurrent access and scalability. It supports the NFS protocol, making it ideal for applications that require shared access to file storage.

Amazon S3 (Simple Storage Service) is an object storage service and is not designed for file system operations that require concurrent access like traditional file systems. While S3 can store and retrieve large amounts of data, it does not provide the same file system semantics needed for multiple instances to access the same files simultaneously.

AWS Artifact is a compliance resource tool that provides access to AWS compliance documentation and does not provide any storage capabilities. It is not relevant to the use case of shared file systems for EC2 instances.