Amazon S3 Glacier Flexible Retrieval is designed for long-lived, infrequently accessed data where retrieval times of minutes to hours are acceptable. It offers very low storage cost per GB while still supporting faster retrieval than archival tiers that can take many hours or days.

The requirement states that data is rarely accessed and must be retrievable within 12 hours. Glacier Flexible Retrieval meets this retrieval-time requirement and is more cost-effective per GB than Standard and Infrequent Access storage classes for long-term, rarely accessed data.

S3 Standard, S3 Standard-IA, and S3 One Zone-IA are optimized for more frequent or lower-latency access and have higher storage cost per GB compared to Glacier Flexible Retrieval.