It feels like you have to be a very big business for this to be a problem that is worth the extra engineering effort vs a single instance with an SQLite file that you backup externally with a cron job
Most stick trading systems and even many banking systems have availability like 40%, going offline outside business hours. But during these business hours they are 99.999999 available.
Usually operation without trouble is operation with plenty of resources to spare, and in absence if critical bugs.
It feels like you have to be a very big business for this to be a problem that is worth the extra engineering effort vs a single instance with an SQLite file that you backup externally with a cron job