We have a couple of tables with about a billion rows now on single nodes in mysql. 256GB RAM and a number of 2TB nvme drives. It works completely fine, but you can forget about timely restore if something goes completely fucked. And we cant do any operation that isnt directly using the index or the whole performance suffers immediately. Which means we basically have to use those tables like they are a distributed database, but at least we have transactionality.