title: How to store user information with DynamoDB and Cognito using Facebook authentication with iOS SDK
body: <p>Is it appropriate to combine <code>Cognito</code> identity management with <code>Dynamo DB</code>?</p>
  
  <p>I would like to authenticate <em>users</em> with <strong>Facebook</strong>, which I can do with <code>Cognito</code> and then store user related data in a <code>DynamoDB</code> table.</p>
  
  <p>What information would I use from <code>Cognito</code> as a <em>primary key</em> for my table to guarantee unicity? Or should I simply use the <em>facebookId</em> that I can get with the <em>graph API?</em>  </p>