Congestion vs. time is definitely a hard problem. We've done an enormous amount of tuning to make this work, and the upcoming Raft release does even more. This part has been quite solid for a while, so I think you might have a better experience with RethinkDB than what you're used to.

There is currently no other way to prime the node -- I hope we don't have to add it. This sort of functionality should work out of the box.