[goatinaboat]

It's a realtime service with second-SLAs that needs to know where you are, where the closest 20 drivers are, the map of the area, places of interest and a dozen other things - for millions of users in hundreds of cities

No it doesn’t. For a start there is no overlap between cities, so that’s easy to shard. And secondly that’s not what SLA means - how many 9’s do you think would be in a sub-second SLA? Thirdly Uber offloads it’s payment to third parties, unless I blinked and it’s issuing its own credit cards now.

You seem to be incredibly impressed by Uber’s tech but have you considered that everyone else’s tech works so well that you just take it for granted? No Uber ride comes close to the complexity of sending a package internationally, and orders of magnitude more packages are sent every day than Uber does rides.