A company plans to migrate an on-premises legacy application to AWS. The application ingests customer order files from an on-premises ERP system and uploads them to an SFTP server. The existing ERP system is already connected to the AWS account. The new application must integrate with the ERP system, be secure and resilient, use SFTP, and process orders immediately when files arrive. Which solution meets these requirements?

The correct solution uses an AWS Transfer Family SFTP internal server in two Availability Zones for high availability and secure, private connectivity with the on-premises ERP system, as the ERP is already connected to AWS. Storing files in Amazon S3 provides scalable and durable storage. An AWS Lambda function processes order files immediately, triggered by a Transfer Family managed workflow, which automates actions upon file upload. The first incorrect option uses an internet-facing server, which is less secure for an ERP already connected to AWS, and S3 Event Notifications are not the most direct way to trigger processing from Transfer Family. The second incorrect option uses Amazon EFS, which is not ideal for this use case compared to S3's durability and scalability, and a single Availability Zone reduces resilience. The third incorrect option uses Amazon EFS and relies on periodic polling with EventBridge Scheduler, which does not meet the requirement to process orders immediately.