> On the one hand, it's hard to scale a system without making it distributed at some point and consistency in distributed systems is really difficult Banks hav

> On the one hand, it's hard to scale a system without making it distributed at some point and consistency in distributed systems is really difficult Banks have scaled systems like this with mainframes and COBOL for decades. It's probably not as hard as you think to get it right if you have your priorities straight. IMHO, for banking, you need to KISS and avoid all unnecessary complexity (especially in the name of "scale"), at least for your master source of truth.