Sort of. One of the requirements was replication. The databases had to replicate every document so that it was stored on two different nodes. This ensures avail

Sort of. One of the requirements was replication. The databases had to replicate every document so that it was stored on two different nodes. This ensures availability. The only way to do that with MongoDB is to run secondary nodes too. Now, it's possible to do say 4 primary and 4 secondaries, but performance would go down because only 4 nodes could do the writing. The problem is that it rarely works out. It's fine at first, but down the road...