Amazon S3 Files, 3 Key Considerations Before Adoption

Amazon S3 Files, which became generally available in April 2026, allows S3 buckets to be used like a filesystem, and can be mounted across four compute environments: EC2, ECS, EKS, and Lambda.

The most important point to watch when adopting it is the cost structure. File read and write operations are billed in minimum 32 KiB units regardless of the actual data size. Measured results show that when writing 100 files of 1 KiB each, even though the actual data is 100 KiB, about 3.125 MiB is billed, resulting in roughly a 32x cost spike.

Therefore, large-scale workloads involving small files with an average file size under 32 KiB may become a cost anti-pattern, so caution is needed. In addition, when reading files of 1 MiB or larger, the request is processed as a standard S3 GET request and only metadata costs are billed, meaning the billing mechanism varies depending on file size.