title: How to check the validity of the credentials from Amazon Cognito at server side(java)
body: <p>Now I am developing some iOS app. This app uses Amazon Cognito to make each user's authenticated id and credentials.</p>
  
  <p>On the other hand, this app uses my original WebAPI server. I want to check the user's validity on the server by using Cognito id and/or credentials.</p>
  
  <p>Which AWS API should I use for this validation at the server(java code)?</p>