I would actually recommend a hybrid approach. If you don't need too much memory there is a cpu heavy Amazon instance that you should scale up and down and have a VPN between a dedicated co-lo machine that handles the base load. If you need memory and cpu, its going to be costly to use EC2 unless you pay upfront for dedicated instances. In this case though the economics are probably not as favorable as getting some co-lo servers and letting them rot away. In short you will need to do a cost benefit analysis to see what makes sense.
For our service we are going to use a co-lo server for our processing with an Elastic Beanstalk frontend and use a VPC + OpenVPN setup to bridge the two. We will incur some bandwidth charges because of this, but the cross talk between the boxes is actually minimal, since the client will post directly to the co-lo box(es) when it needs to upload, etc.
For our service we are going to use a co-lo server for our processing with an Elastic Beanstalk frontend and use a VPC + OpenVPN setup to bridge the two. We will incur some bandwidth charges because of this, but the cross talk between the boxes is actually minimal, since the client will post directly to the co-lo box(es) when it needs to upload, etc.