title: Single page apps keeping client and server in sync
body: <p>I am trying to understand how single page apps spa's work.</p>
  
  <p>My understanding of a spa is that you load the data on start-up and you use ajax calls for save etc, and the whole idea is that your models cache data on the client so you have a rich snappy experience in your browser.</p>
  
  <p>I am confused as to how the client stays in sync with the server changes.
  E.G. If I have multiple users logged into my spa and they are all making changes, how does my client know that another user has updated a persons details if it is using cached data?</p>
  
  <p>My guess is that something similar needs to happen server side to update the client on a change. Does this exist or am I misunderstanding something?</p>
  
  <p>Any help or pointers to additional info would be much appreciated.</p>
  
  <p>Thank you in advance.</p>