I think you’re asking a rocket science question, there are inly rocket science answers.
Sql Database operations need to happen in order, the previous operation needs to have updated the state before a new one can be done… you can sync to another though for the read operations.. to mostly happen from a mirror.
keeping lots of it in ram can improve speed but hard to do that distributed - perhaps with sharding. this isn’t the right hardware though if you really want speed. One more powerful x86 cpu with a heap of ram will wipe the floor on speed & even power efficiency. These systems are great for just small scale testing of stuff