database – Saving users interactions

I am creating an app with flutter and Im trying to save a users interactions, for example, the user can join different groups and access them, have them available when they log in. I am using AWS Amplify to authenticate the user. I know this is process used in nearly every app, so maybe Im missing an obvious way to achieve this. However, I am new to developing and still trying to learn, what the processes and practices are.

My first idea was to save the “Groups” ID with the users account, find and load that when the user log in. This “Group” will be stored on a server, referenced by an ID. Is there a better way, or documentation anyone could point me in the direction of. Does Amplify already store what the user does?

I am developing this app with Flutter and using AWS Amplify as the backend.

Thank you for any help and your time!