You have a choice. If the "autopublish" package is added to your project, which it is by default, then the entire dataset is sent to the client. That's good fo

You have a choice. If the "autopublish" package is added to your project, which it is by default, then the entire dataset is sent to the client. That's good for learning and prototyping, but isn't any good for production use. The Leaderboard example uses autopublish. Once you app works and you're ready to lock it down and scale it up -- and only then -- you remove the autopublish package. Now, it's up to you to define what's sent to the client. Use Meteor.publish() on the server to set up different datasets that clients are allowed to subscribe to, and use Meteor.subscribe() on the client to turn on/off a particular dataset. The Todos example demonstrates this -- it retrieves just the items for the todo list you're looking at, plus the list of lists. It's just a couple of lines of code, like 5 or 10, and not tricky ones either.