How to Proxy, Remoting, HttpTunnel, through IIS

How to Proxy, Remoting, HttpTunnel, through IIS

I'm not sure of the best solution to this problem. The current network is
setup as:
Web server => Cms server => DB server
This is an existing setup for security reasons and cannot change. The Web
server is connected to the internet, and can connect to the Cms server but
not the DB server. The Cms server can access the DB server. (The idea was
if the Web server got hacked, they would have to get past the Cms Server
before getting to the DB server)
My current implementation to the problem as to create a simple proxy on
the Web server, with the website on the Cms server (as the website need to
access the DB). This works ok but i have timeout issues randomly. I've
written the proxy in MVC and its very simple and works. Is this the best
solution or is there a better way to solve this.