A solutions architect must design storage for client case files that are core company assets. The number of files will grow over time. Multiple EC2 application servers must be able to access the files simultaneously, and the solution must provide built-in redundancy. Which solution meets these requirements?

Amazon EFS is the correct choice because it provides a scalable, shared file system that multiple EC2 instances can access concurrently using the NFS protocol. It offers built-in redundancy across multiple Availability Zones, ensuring high availability and durability for the growing number of case files. Amazon EBS volumes are block-level storage attached to a single EC2 instance, not suitable for shared access. Amazon S3 Glacier Deep Archive is an object storage service designed for long-term archival with infrequent access, not for active file system use by applications. AWS Backup is a backup service, not a primary storage solution for active application data.