This might seem like bait but I assure you it isn't - I reach for MySQL by default over postgres - but why did you choose MySQL for the state database? In terms of HA and synchronous clustering it's a good solution but unless I'm misreading it seems like you only use it for a key value store and for an append only log, neither of which are necessarily the problems you think "MySQL" for.

Given what seems to be a pretty fashionable stack (kubernetes, using etcd directly, cloud first, IaC and custom database technology) I'm interested what a company like that reaches for MySQL. Was the MySQL cluster already deployed for other reasons?