>It manages do that while working in 70+ countries over 15,000 cities with multiple different languages and payment vendors and it is all done via a single application.

I'd assume almost all of that is done server side though. Most likely the app is mostly just a wrapped website with some gps and notification code on top.

And as someone who works on platform that makes use of numerous payment portals depending on the product and region you're buying in. It's all just wrapped up in logic AKA if statements.