title: How to link developer authenticated user across devices in Cognito
body: <p>I'm just trying to get a handle over this framework and I want to confirm that my approach is correct.</p>
  
  <p>I can authenticate my own user using the method: <code>getOpenIdTokenForDeveloperIdentity</code> and supplying an <code>IdentityPoolId</code> and a Logins key-pair with my Developer provider name and a token which I provide.</p>
  
  <p>Now, from what I understand, when the user logs into a second device, in order for Cognito to understand that this is the same user, I have to provide it with an IdentityId. However, I'm not sure of the best way to get the <code>IdentityId</code> programmatically so that it will match up with the initial login. </p>
  
  <p>The only technique I can think of is to store the <code>IdentityId</code> in my own DB and provide my own method for retrieving it. Is this the best way? Or should I be working with this framework differently? </p>
  
  <p>I'm still a beginner to AWS in general and I'm just trying to understand the best practices for this framework. </p>
  
  <p>BTW, I'm implementing the Android SDK and the PHP SDK for my backend.</p>