I want to make my web app fast, especially the first page load (index.html).
Can I do this by hosting myfastapp.com on Rackspace CloudFiles and then have a subdomain called nodeserver.myfastapp.com which connects to a Node Server on Joyent.
Note: The node server will only connect via socket.io to tell the client which additional files to grab from the CDN (myfastapp.com).
There's a guide for this in the Cloud Files docs at Create Static Website.