Eh, they're solving different problems. I don't think you can necessarily call Uber's problem more complicated just because it's an order of magnitude more volume. I worked at a small ad tech start-up with a team of 5 engineers on a real-time bidding platform that was serving 1k requests/second and moved to a travel company that's now 100+ engineers that serves maybe ~250 requests/second at peak traffic, but the travel company's infrastructure is a lot more complicated even though the volume is smaller.