This is a simple http proxy that may be usefull for you. You can use it on your own http server, express app, or with the stand alone script. For examples see the examples dir.
$ npm install simple-proxy
page: proxy [options] Options: -h, --help output usage information -v, --version output the version number -L, --listen <port> listen to port  -M, --mount <mount> proxy request starting with this pathname -H, --host <hostname> to this hostname -P, --port <port> to this port
$ proxy -M api -H remote-api.com /var/www/the_site
This will serve the files located in /var/www/the_site on the default port, 3000.
All request that begins with /api, will be proxy to remote-api.com, and not served from the local files.
If you need something just tell!!... :)