title: Implementing dynamically updating upvote/downvote
body: <p>How to implement dynamically updating vote count similar to quora:- Whenever a user upvotes an answer its reflected automatically for every one who is viewing that page.</p>
  
  <p>I am looking for an answer that address following:</p>
  
  <ul>
  <li>Do we have to keep polling for upvote counts for every answer, If yes
  then how to manage the server load arising because of so many users<br>
  polling for upvotes.  </li>
  <li>Or to use websockits/push notifications, how scalable are these?  </li>
  <li>How to store the upvote/downvote count in databases/inmemory to support this. How do they control the number of read/writes. My backend database is mysql</li>
  </ul>
  
  <p>The answer I am looking for may not be exactly how quora is doing it, but may be how this can be done using available opensource technologies.</p>