What are the strategies to sync with remote storage?

I'm complete newbie, just desiging a collaboration system.

My current scheme looks like - multiple clients connected through socketio to rabbitmq broker, which routes messages between them. When one client have some changes, it will send them through socketio to all who needs.
Ok, but when should I sync it with database?
Simpliest way - sync all changes, but it will be CPU consuming. I have some other ideas, but don't like them :)