RocksDB has support for Ztd and preset dictionaries and it makes sense since it has the same kind of level-spans chunking being a fork of LevelDB. Entries are

RocksDB has support for Ztd and preset dictionaries and it makes sense since it has the same kind of level-spans chunking being a fork of LevelDB. Entries are stored in-memory/logged (instead of put into a b-tree like classic DB's) and then periodically placed in span-files that are "linear" for faster search, however as these span files are built in bulk it makes more sense to compress blocks of them since much data is handled at once (so even if it's linear it's still blocks and reading just produces more variable size blocks by decompression upon read).