title: Scalable voting system with MongoDB
body: <p><a href="http://cookbook.mongodb.org/patterns/votes/" rel="nofollow">This article</a> explains very clearly how to implement a voting system with MongoDB, and to limit one vote per user and per object.</p>
  
  <p>I have one extra requirement. I need the votes of a given user to be visible for the objects displayed. For example, if I am displaying 20 tweets, and the user has voted on 3 of those tweets, I want those votes to be visible. (For example, using a green up-arrow.)</p>
  
  <p>One solution is to send to the client, for each question, the set of voters. Another solution is to send to the client the set of votes he has cast. I do not see either solution as a scalable one. Any suggestions?</p>