An on-premises SaaS provider accepts several files daily via multiple public SFTP endpoints. Customers have added the SFTP endpoint IP addresses to their outbound firewall allow lists and cannot change those allowed IPs. The company wants to migrate to AWS and reduce operational overhead while preserving the existing source IPs customers allow. Which solution satisfies these requirements?

The correct solution leverages Bring Your Own IP (BYOIP) to import the existing public IP addresses into AWS. This is crucial because customers have those IPs on their firewall allow lists and cannot change them. AWS Transfer for SFTP is the ideal service for hosting SFTP endpoints, as it is a fully managed service that reduces operational overhead and integrates directly with Amazon S3 for file storage. Allocating Elastic IPs from the BYOIP pool to the AWS Transfer for SFTP endpoint ensures the service is accessible via the familiar, pre-approved IP addresses. Incorrect options: Using an Application Load Balancer (ALB) with EC2 instances running FTP services is less ideal because ALBs do not natively support FTP/SFTP, and managing EC2 instances increases operational overhead. Storing files on EBS volumes also adds management complexity compared to S3. Registering the IP block with Route 53 and using a Network Load Balancer (NLB) with EC2 instances for FTP still involves managing EC2 instances, which goes against the goal of reducing operational overhead. S3 VPC endpoints do not support SFTP directly, and S3 buckets do not have native SFTP support. This option is fundamentally incompatible with the requirement for an SFTP endpoint.