RocksDB is an embedded database engine. MyRocks and MongoRocks are RocksDB storage engines for MySQL and MongoDB. All of this is open-source. Facebook started these projects to get better performance, efficiency and compression with fast storage devices like flash-based SSD but they also work great with disks. Using RocksDB we are able to significantly save space and reduce the device write rate which allows us to use less flash storage for much longer. MongoRocks is in production and has allowed us to reduce space usage dramatically. MyRocks is being actively developed at Facebook. RocksDB is used extensively in production at Facebook and numerous other companies.