Isn't it your own article?
31 karma · joined July 7, 2009
it's my understanding that mongo currently only shards primary key lookups, not queries. it'll be interesting to see how successful they are in grafting a full distributed layer over top of it. generally the merge layer kills you because you must query all nodes to support global indexes. that is not to say that its impossible.
mongo has some wacky stuff in the on-disk file format which is kind of interesting, too.
I find it strange that everyone trotted out their preformed opinion for this piece, but no one comments on the cassandra article which actually proposes a solution...although it requires you to learn something, how horrible.