If you've been paying attention to the MongoDB world lately, then you know that exciting things are afoot. The 3.0 release introduces a modular storage engine API, allowing third party engines like RocksDB, TokuDB and WiredTiger to integrate seamlessly with the MongoDB data interface. The RocksDB engine developed by Facebook engineers is one of the fastest, most compact and write-optimized storage engines available. RocksDB has been running for years as a storage layer for various services here at Facebook, so we have a lot of confidence in its maturity. It is also currently the only LSM engine available for use with MongoDB (WiredTiger also supports LSM natively, but only the B-tree implementation will be available for MongoDB until later releases). At Parse we have been working closely with other Facebook engineers to integrate and optimize RocksDB + MongoDB, by replaying a wide range of production workloads offline and comparing results between mmapv1, RocksDB, and WT. And we now