MongoDB Schema Design - Real-time Chat
- by Nick
I'm starting a project which I think will be particularly suited to MongoDB due to the speed and scalability it affords.
The module I'm currently interested in is to do with real-time chat. If I was to do this in a traditional RDBMS I'd split it out into:
Channel (A channel has many users)
User (A user has one channel but many messages)
Message (A message has a user)
The the purpose of this use case, I'd like to assume that there will be typically 5 channels active at one time, each handling at most 5 messages per second.
Specific queries that need to be fast:
Fetch new messages (based on an bookmark, time stamp maybe, or an incrementing counter?)
Post a message to a channel
Verify that a user can post in a channel
Bearing in mind that the document limit with MongoDB is 4mb, how would you go about designing the schema? What would yours look like? Are there any gotchas I should watch out for?