I've deployed Serv-U like this for a number of customers.
1) The AWS (Amazon Web Service) you'll be using is EC2 (Elastic Compute Cloud), which essentially spins up on-demand Windows or Linux VMs of your choice.
2) I like to run Serv-U MFT Server on a 2-core, 4GB-mem Windows 2008 R2 instance (your storage will vary) with the Serv-U Gateway running on 2-core, 4GB-mem SUSE Linux (with the smallest possible amount of storage).
3) If this is going to be a 24/7 server (i.e., production), look into purchasing a "Reserved Instance" (for which you get a much-lower hourly fee in exchange for a one-time, up-front payment).
4) If you're using the Serv-U Gateway, use TWO security groups: one to define the traffic from the Internet to the Gateway, and the second to define traffic from Serv-U MFT Server to the Gateway. (Remember, that connection does NOT go from Gateway to Server!)
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