title: MongoDB index/RAM relationship
body: <p>I'm about to adopt MongoDB for a new project and I've chosen it for flexibility, not scalability so will be running it on one machine. From the documentation and web posts I keep reading that all indexes are in RAM. This just isn't making sense to me as my indexes will easily be larger than the amount of available RAM.</p>
  
  <p>Can anyone share some insight on the index/RAM relationship and what happens when both an individual index and all of my indexes exceed the size of available RAM?</p>