Which storage solution will meet these requirements in the MOST cost-effective way?

Explanations:

Mountpoint for Amazon S3 allows access to S3 as a file system, but it may not provide the low-latency performance required for a media rendering application due to potential network delays and the nature of S3’s eventual consistency model.

An Amazon S3 File Gateway caches frequently accessed data on-premises, providing low-latency access while storing the main data in S3. This setup is cost-effective as it minimizes on-premises storage costs and efficiently utilizes S3 for storage.

Copying data to Amazon FSx for Windows File Server introduces additional storage costs and complexity. While FSx provides high performance, it does not address the original requirement of maintaining data primarily in S3 and can lead to increased costs without significant performance benefits.

Setting up an on-premises file server and using the Amazon S3 API can result in higher latency due to API call overhead and potential data transfer delays. This option does not provide the low-latency access needed for the application and can incur additional operational costs.