Oh wow. More MongoDB servers and it did worse? That's really surprising and disappointing for MongoDB.

hmm and good point. It does seem like shard key would be possibly limited to just 1 common query. I haven't really got to that part yet myself, just going by what I've learned so far in the class I'm taking.

edit: oh reread. 2 servers per instance, not the same amount of actual server instances. I wonder if you ran 1 per instance if you'd get better results...

I know the MongoDB people seem to hype it up and some large companies are using it. The system does seem like a good dream if it worksout.