A company migrated its application to AWS. The application runs on Amazon EC2 Linux instances in an Auto Scaling group across multiple Availability Zones. Files are stored on an Amazon Elastic File System (Amazon EFS) file system that uses EFS Standard-Infrequent Access storage. The application indexes the files and stores the index in an Amazon RDS database. The company wants to reduce storage costs with minimal changes to the application and services. Which solution will meet these requirements MOST cost-effectively?

The correct solution leverages Amazon S3 Intelligent-Tiering, which automatically moves objects between access tiers based on access patterns, optimizing costs without performance impact. Updating the application to use the S3 API is a necessary change but minimal compared to re-architecting storage. Deploying Amazon FSx for Windows File Server or OpenZFS would introduce new managed file systems, which are generally more expensive than S3 for general object storage and would still require application changes. Using S3 Glacier Flexible Retrieval directly would be cost-effective for infrequently accessed data, but the "standard retrievals" requirement implies frequent access, making Glacier too expensive for retrieval and potentially impacting performance due to retrieval times. Intelligent-Tiering handles this automatically and cost-effectively.