I have been looking into Node.js, express and Nowjs and love how easy it is to have real time interactions between clients. My background is mostly from CodeIgniter MVC using PHP and MYSql. I want to re make a current web project of mine from scratch to make everything better and more real time with this newer technology.

After researching and doing test examples I want to use node.js , express and Nowjs for the real time interactions once someone connects to the socket.io to pull data back to clients. But use Code Igniter for the control of the site and user management , possible shopping cart/store , pretty much everything else. This is purely due to time constraints and that I am already familiar with doing it that way.

I have been looking at MongoDB as an alternative to MySql, Basically the app is going to be multiple chat rooms all on one page. with the ability of notifications and private messaging. Lots of data transfer and images.

before I started piecing it together I wanted to get people who have already done something similar. My model would use Code Igniter and MySQL to render the page and then connect them onto a node.js server and broadcast using express and nowjs would using a mongoDB be better than mySQL for tons of messages and data being stored or MYSQL? Also does it make since to not make the whole site on Node.js , kinda piece it together like that?