A solutions architect is designing an application that allows business users to upload objects to Amazon S3. The solution must maximize object durability and keep objects readily available at any time for any length of time. Objects are accessed frequently during the first 30 days after upload, with much lower access likelihood afterward. Which solution is MOST cost-effective?

The most cost-effective solution is to store objects in S3 Standard initially due to frequent access in the first 30 days, then transition them to S3 Standard-IA. S3 Standard-IA is designed for data that is accessed less frequently but requires rapid access when needed, offering lower storage costs than S3 Standard. This aligns with the requirement for much lower access likelihood after 30 days while maintaining immediate availability. Storing objects in S3 Glacier is incorrect because Glacier is for archival data with retrieval times ranging from minutes to hours, which does not meet the "readily available at any time" requirement. S3 One Zone-IA is less durable than S3 Standard-IA as it stores data in a single Availability Zone, making it less suitable for maximizing object durability. S3 Intelligent-Tiering is a good option for unknown or changing access patterns, but in this scenario, the access pattern is clearly defined (frequent for 30 days, then infrequent), making a direct lifecycle rule to S3 Standard-IA more cost-effective than Intelligent-Tiering's monitoring overhead.