MongoDB Structure for message app

I see that this question is old, but for anyone interested, a similar question was asked and one answer looks viable https://stackoverflow.com/a/30830429/132610

Conversation : { id: 123, members: [ user_id1, user_id2 ]}Message { conversationId: 123, author: user_2, body: 'Hi what's up' }Message { conversationId: 123, author: user_1, body: 'Whanna ask some question on stackoverflow' }

Update #1

1) Scalability: MongoDB scales well with very large collection. Billions of messages per collection. There is a technique called sharding that can allow you to split larger collection to multiple nodes.

2) Reading. Since MongoDB has indexing mechanisms, reads are comparable to any fine-tuned database engine. So reading will not be an issue. Especially, when a conversation(group|room) has fewer participants, for example two people messaging each other.

Your question is really one of schema design. I suggest taking a look at this page on MongoDB schema design to get a sense of the choices and trade-offs: http://www.mongodb.org/display/DOCS/Schema+Design

In addition, you should probably review the links in the 'See Also' section of that document. I especially recommend the video presentations.

Finally, you should probably take a look at this document for a discussion of the three possible schemas for a messaging/commenting database, including the trade-offs for each design: http://docs.mongodb.org/manual/use-cases/storing-comments/

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 123124messages: [         { 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        }       ]}