Great explanation, and I agree with one caveat - from my experience if you get to a truly large single RDBMS you have already lost, even if you have a powerful

Great explanation, and I agree with one caveat - from my experience if you get to a truly large single RDBMS you have already lost, even if you have a powerful enough machine to run it on. Massive RDBMS instances are awful to manage. Hard to backup/restore/fork. Hard to migrate tables and schemas without causing downtime. Accidental downtime happens all the time due to locks, bad indexes, bad query plans , etc etc. at large scale they are capricious beasts, care and feeding and most importantly changing them becomes a dark art. Don’t let them get too big you’ll regret it :)