Architecture overview
Ultimately behind-the-scenes ServiceStack is just built on top of a set of Raw ASP.NET IHttpHandler's. There are 2 distinct modes in any ServiceStack web service 1) Configuration mode, which only gets run when configuring and registering your AppHost and 2) Runtime mode which gets run on every request.
The entry point for ASP.NET and HttpListener requests is in the ServiceStackHttpHandlerFactory whose purpose is to return the appropriate IHttpHandler for the incoming request.
ServiceStack's RestHandler shows what happens during a typical ServiceStack request:
