TiDB and CockroachDB both use Facebook's rocksdb. I would not call it an unproved KV store. Both also use etcd's raft implementation which is also quite well proven.
Sure, but I wouldn't exactly call them mature yet. I think MySQL is still much easier to trust than RocksDB. (I don't actually know much about RocksDB, but I remember that LevelDB had a bunch of data corruption issues. Hopefully RocksDB doesn't.)
To quote the famous video[1]: "Relational databases have been around since the fucking 70s and are some of the most mature technology you can find."
RocksDB is widely used in many of projects for years, i think it's quite mature. Not just TiDB and CockroachDB, MyRocks and MongoRocks are using RocksDB as storage engine too. Also there are plenty of other projects are using RocksDB. If you are worry about the adding new feature of RocksDB, yes, you are right, but all of the storage engine are changing rapidly(even InnoDB which is used by MySQL as default engine), Anyway, happy hacking :)
