I am in the process of building a Web Service API for my application.
Also, I am planning to expose the Service via both REST and SOAP.

I'm interested in getting some feedback from the community as to which programming language I should choose to implement the service? (I know C#, Java and Ruby - RoR well enough to create the service).

The service is mainly an HTTP POST service.
It will need to handle around 2000 concurrent connections as well as be able to handle around 10,000 HTTP POST's per second. (for SOAP we will have a submit method for the clients to call).

The service does not return any response to the client for the POST requests.

Any ideas on which programming language/architecture which should be used?