How can I create a friend system using AWS for Android?

So I'm developing an app that requires for me to implement a friend system, in which permissions will be different amongst users who are "friends". I am using AWS Cognito for identity management, and DynamoDB for my database.

In my case, I will be granting view permissions only to confirmed friends of the user; you know, the standard run-of-the-mill friend settings. Can anyone point me in the right direction as to how to approach this? I am not entirely sure how to handle the issue of setting permissions for particular and individual users within my User Pool, especially in regards to particular and individual recipient users.