Correlation between Service Instances and Web Traffic

Question

So I'm digging into AppFog's pricing sheet and I am struggling to figure out which one I need. here

Several questions

1. What is a service instance?
2. How do I somehow translate "service instance" to web traffic capabilities?

I am deploying a web app soon and looking at something to handle serious traffic (around a million users a month)

Answer 1

Being in a similar situation as you I think that a possible hint is the Pagodabox traffic visualizer. Also from one of the Pagodabox user stories I've concluded that having 16 service instances with 400 MB RAM each can handle 1M users (assuming that you have a reliable DB, and probably using Memcached).

(In AppFog the Services menu in the admin portal is really misleading - count instances in the Applications menu)