A company wants to build a logging solution for its multiple AWS accounts. The company currently stores the logs from all accounts in a centralized account. The company has created an Amazon S3 bucket in the centralized account to store the VPC flow logs and AWS CloudTrail logs. All logs must be highly available for 30 days for frequent analysis, retained for an additional 60 days for backup purposes, and deleted 90 days after creation. Which solution will meet these requirements MOST cost-effectively?

The most cost-effective solution is to transition objects to S3 Glacier Flexible Retrieval after 30 days and then delete them after 90 days. For the first 30 days, logs are frequently accessed, so they should remain in S3 Standard. After 30 days, the requirement changes to "retained for an additional 60 days for backup purposes," implying less frequent access. S3 Glacier Flexible Retrieval is significantly cheaper than S3 Standard-IA for infrequently accessed data that needs to be retained for a longer period, making it ideal for the backup phase. Finally, an expiration action ensures deletion after 90 days, meeting the retention policy. Incorrect options: Transitioning to S3 Standard after 30 days is not cost-effective for data that is no longer frequently accessed. Moving to S3 Standard-IA and then S3 Glacier Flexible Retrieval after 90 days is incorrect because the requirement is to delete after 90 days, not move to another storage class. Also, S3 Standard-IA is more expensive than S3 Glacier Flexible Retrieval for the backup phase. Transitioning to S3 One Zone-IA and then S3 Glacier Flexible Retrieval after 90 days is incorrect for the same reason as the previous option regarding the 90-day deletion. Additionally, S3 One Zone-IA offers lower durability and availability than S3 Standard or S3 Glacier Flexible Retrieval, which might not be suitable for backup purposes.