I've used Django with "real data", as in accountancy software for multiple years of transactions across 200+ fairly large clients and it's absolutely fine.

Whereas I've used Sqlalchemy and getting it to do a basic join, turns out there's 3 different ways of doing it all with an insane amount of crap to find the right way of doing things. I actually left my old job in part due to Sqlalchemy being too painful to work with.