A company has an on-premises business application that generates hundreds of files per day. These files are stored on an SMB file share and require low-latency access for the application servers. A new company policy requires that all application-generated files be copied to AWS. There is already a VPN connection to AWS, and the application team cannot modify the application code. Which service should a solutions architect recommend to allow the application to copy files to AWS?

AWS Storage Gateway is the correct choice because it provides a hybrid cloud storage solution that seamlessly connects an on-premises environment with AWS cloud storage. Specifically, its File Gateway configuration allows you to present an SMB file share to your on-premises application, which can then write files to it as usual. Storage Gateway then asynchronously uploads these files to Amazon S3, meeting the requirement to copy files to AWS without modifying the application. This approach leverages the existing VPN connection and provides low-latency access for the application servers to the local cache. Amazon EFS is a fully managed NFS file system in AWS, not designed for on-premises SMB access. Amazon FSx for Windows File Server is also a fully managed file system in AWS, but it's primarily for cloud-native Windows workloads, not for bridging on-premises SMB writes to AWS. AWS Snowball is a data migration service for large-scale data transfers, not for continuous, incremental file synchronization.