IIRC, MySQL (and PosgreSQL) is pretty much limitted to a write/read-replica sort of horizontal scaling. Other SQL engines have better support for multi-master configurations.

However, these types of configurations are usually tied to licensing - especially for Microsoft SQL server and OracleDB.

As another commenter suggested, there is Yugabyte and CockroachDB as well - of those two I think CockroachDB is the more mature product. And they're one of the fiercest competitors for the company I work for too.

I cannot speak to "Battle Tested-ness" of CockroachDB, but given it's been around for a few years now, I don't think it's quite as risky as other comments have indicated. Also, they're doing something right if we haven't been able to convert many CockroachDB customers.