RocksDB is more compact storage-wise when records are small. Notice here http://symas.com/mdb/ondisk/ http://symas.com/mdb/ondisk/ that RocksDB space is smaller

RocksDB is more compact storage-wise when records are small. Notice here http://symas.com/mdb/ondisk/ http://symas.com/mdb/ondisk/ that RocksDB space is smaller using 24 byte values, but same or larger at 96 byte values. By the time you get to 768 byte values, LMDB is smallest.