Data Model for a popular/basic type of social app

I am trying to learn about Google Datastore and creating a basic application to have some practical experience with it opposed to just reading the docs. I would like to create a basic social application where users can send messages to their friends and view the messages their friends have sent them. My Basic App Requirements: **Users Section:** - A user registers to the app. The user can then log in by using their username/email and checking if the password is correct and the status must be VALID and not something like DEACTIVATED. - A user can also be deleted. When a user is deleted If a user deletes their account their references from all their friends need to be removed and messages needs to be removed (or hidden). This is obviously expensive. *Users Model* -username (need to be able to make equality searches on this field. e.g select * from kind where username = 'Bob') (index) -email (need to be able to make equality searches on this field. e.g select * from kind where email = 'Bob@gmail.com') (index) -fullname -password -status (need to be able to make equality searches on this field. e.g select * from kind where status = 'DEACTIVATED') (index) -time_created **Friends Section:** - A user can query to find all of their friends (Accepted and Pending). - A user can add another user to be friends (make sure relationship doesn't already exist and make sure user exists). - A user can accept/reject a friend request. - A user may have a max of 100 friends. *Friends Model* -User1 (index) -User2 (index) -status -time_created **Messages Section:** - A user may see all the messages they sent/received to/from confirmed friends - A user can send a message to a confirmed friend. - A user may receive a message to a confirmed friend. - Messages will be paginated in the application so 10 messages at a time come up sorted by the newest coming first. *Messages Model* -from (need to be able to make equality searches on this field. e.g select * from kind where from = 'Bob') -to (need to be able to make equality searches on this field. e.g select * from kind where to = 'Bob') -msg -time_created (need to sort on this so that the newest messages come first) My plan is to make 3 kinds: Users, Friends, and Messages (each would have the attributes shown above). Some concerns I have is regarding atomic operations. For users, would it be wiser to create a one way relationship between friends or two-way. If two-way, say the friends request gets accepted or rejected, would the application be atomic? Another question is if a user gets removed, how best to handle this to be inexpensive and keep data consistent. Is this a good model for this basic/popular type of social application? I am very interested to hear of anyone suggestion how they would implement this basic application and the reasons why. Cheers!