MongoDB Structure for message app

Question

I am breaking my mind up thinking about a good document structure for handling a message app.

I basically need three (or four) types of objects:

1. The user (

Answer 1

Please find my suggestion:

    Person : {
        person_id: '123',
        last_login: 12.06.2008,
        online: true
    }

Conversation : {
 conversation_id: append the greater person_id to the lower person_id, // person_1_id =123 and person_2_id =124 then its 123124

messages: [ 
        { message_id: 1, 
          message_text : 'Hi what's up',
          sender_id : 123,
          receiver_id: 124,
          timestamp : 12344567891
        },
        { message_id: 2, 
          message_text : 'fine',
          sender_id : 124,
          receiver_id: 123,
          timestamp : 12344567891
        }
       ]
}