I find that stuff like this works best with no database whatsoever. There's no particular reason to store cursor positions for longer than it takes to route messages, so you can keep them in memory.

Try writing something like this, and you'll be surprised how easy it is. Especially with some of the new frameworks that are built specifically for it (ie., node.js). I expect this to be the "Hello World" for realtime web apps, much in the way that little chatrooms were the "Hello World" for java and sockets.

I have written stuff like this in node.js that's why I suggested it as one of the options he would typically use for this.

I figured he'd either send directly from one host to another with node.js or poll redis.