A company's application generates many files (~5 MB each) stored in Amazon S3. Company policy requires retaining the files for 4 years before deletion. Files must be immediately accessible at all times and are frequently accessed during the first 30 days but rarely after. Which storage lifecycle solution is MOST cost-effective?

The correct solution is to transition files from S3 Standard to S3 Standard-Infrequent Access (S3 Standard-IA) after 30 days and delete them after 4 years. S3 Standard-IA is designed for data that is accessed less frequently but requires rapid access when needed, which matches the requirement for immediate accessibility. It offers lower storage costs than S3 Standard, making it cost-effective for data accessed rarely after the initial 30 days. Moving to S3 Glacier is incorrect because Glacier is for archival data where retrieval times can be minutes to hours, violating the "immediately accessible at all times" requirement. S3 One Zone-IA is less resilient as it stores data in a single Availability Zone, which may not meet typical business requirements for durability unless explicitly stated. The option to move to S3 Glacier after 4 years is incorrect because the files need to be deleted, not archived further.