title: Implementing fraud-proof voting system using SimpleDB
body: <p>I'd like to implement a voting system with all data stored in Amazon SimpleDB. The frontend is also running on Amazon EC2. My main concern is cost of the service.</p>
  
  <p>The voting system needs to be fraud-proof. That is, each visitor is only allowed one vote per election and there are no user accounts. I have considered storing a SimpleDB item for each vote along with the ip address it came from. Then I would only insert a new vote if there is no entry for that ip/election pair.</p>
  
  <p>However, this sounds very expensive in terms of storage and processing. I would have to retrieve all votes to tally them up to display an up to date result.</p>
  
  <p>The other option I have considered is storing the votes and only occasionally summing them up and caching the result. But this still requires me to store all of the votes.</p>
  
  <p>What is your recommendation? </p>