I want to program my back-end side of my game by Node.js.

Back-end stuffs of my game are 1) Login and Registration 2) Profile 3) Sending message to other users and Inbox 4) Sending Notification 5) Set some information i.e. store information or any other things

Now I want to know Node.JS is suitable or not ? I've watched some tutorials about Node.js before.

I know a little about Socket.io too. So I think by myself combining Node.js and Socket.io is good in Unity3D.

The second question is which data base should I use ?