A company runs multiple Amazon EC2 Linux instances across two Availability Zones in a VPC. The applications use a hierarchical directory structure and must read and write rapidly and concurrently to shared storage. What should a solutions architect do to meet these requirements?

Amazon EFS is a scalable, elastic, cloud-native NFS file system that can be mounted concurrently by multiple EC2 instances across multiple Availability Zones. This directly addresses the requirement for shared storage with rapid, concurrent read/write access and a hierarchical directory structure. Amazon S3 is object storage, not a file system, and does not support concurrent mounting with a hierarchical directory structure in the same way EFS does. EBS volumes are block storage, designed to be attached to a single EC2 instance at a time (with some exceptions like Multi-Attach for io2, but not for concurrent file system access across multiple instances/AZs without complex layering). Synchronizing multiple EBS volumes would introduce significant complexity and potential for data inconsistency, failing to meet the simple shared storage requirement.