An application runs on multiple Amazon EC2 instances that access a shared file system simultaneously.

 Amazon Elastic File System (Amazon EFS) is the AWS storage service that should be used for an application that runs on multiple Amazon EC2 instances that access a shared file system simultaneously. Amazon EFS is a fully managed service that provides a scalable, elastic, and highly available file system for Linux-based workloads. Amazon EFS supports the Network File System version 4 (NFSv4) protocol and allows multiple EC2 instances to read and write data to the same file system concurrently. Amazon EFS also integrates with other AWS services, such as AWS Backup, AWS CloudFormation, and AWS CloudTrail. For more information, see What is Amazon Elastic File System? and [Amazon EFS Use Cases].