At 6:30pm EST, we determined the most effective course of action was to re-index the shard, which would address the memory fragmentation and usage issues. Soun

At 6:30pm EST, we determined the most effective course of action was to re-index the shard, which would address the memory fragmentation and usage issues. Sounds similar to some of the problems we're facing with MongoDB too. Indexes fragment a lot, especially if you delete documents frequently. You have to reindex everything eventually. MongoDB offers background indexing (except for _id fields!) but it's not really an option if you need the indexes at all times to keep executing queries. Also, you'll need to reindex _id eventually and there's currently no way to do that without blocking the server.