How do I manage MongoDB connections in a Node.js web application?

I’m using the node-mongodb-native driver with MongoDB to write a website.

I have some questions about how to manage connections:

1. Is it enough using only one MongoDB connection for all requests? Are there any performance issues? If not, can I setup a global connection to use in the whole application?

2. If not, is it good if I open a new connection when request arrives, and close it when handled the request? Is it expensive to open and close a connection?

3. Should I use a global connection pool? I hear the driver has a native connection pool. Is it a good choice?

4. If I use a connection pool, how many connections should be used?

5. Are there other things I should notice?