It's interesting that they don't break the problem apart geographically. It's inherent in Uber that you're local. But their infrastructure isn't organized that way. Facebook originally tried to do that, then discovered that, as they grew, friends weren't local. Uber doesn't need to have one giant worldwide system.

Most of their load is presumably positional updates. Uber wants both customers and drivers to keep their app open, reporting position to Master Control. There have to be a lot more of those pings than transactions. Of course, they don't have to do much with the data, although they presumably log it and analyze it to death.

The complicated part of the system has to be matching of drivers and rides. Not much on that yet. Yet that's what has to work well to beat the competition, which is taxi dispatchers with paper maps, phones, and radios.