Whatsapp used to service 900 million users with literally 50 engineers. Instagram had 13 employees when it was acquired. The old canard is true if you focus on a core product and make smart architectural choices. (in Whatsapp's case they credit a lot of their efficiency to Erlang).
Simplistic messaging apps aren’t really a good model to run off of. Designing WhatsApp and Instagram are common system design questions because they’re trivial in comparison to design Uber/Lyft, etc.
Even Waze isn't complex enough to compare with Uber. Waze has to process real time data but doesn't have to deal with processing payments and complying to regulations worldwide.
There's a bunch of reasons why this model doesn't hold up in the long run, and I'll give one of them: accessibility. Once your business decides that your app must be sufficiently accessible to reach the many people who need accessibility work, your backlog explodes.
Technically it isn't: if you run an American business, you are subject to the Americans With Disabilities act as it is pursuant to electronic services [1].
Uber specifically would definitely fall under a "public transportation" service - accessibility is non-optional if someone decides to sue. [2]
>> So ignore accessibility. It's not a legal requirement and it doesn't pay.
Firstly that is just plain incorrect in a lot of areas (of business) and jurisdictions. Secondly your outlook on accessibility is just ... SMH and walks away from keyboard.
says who? accessibility is not that hard to achieve if you know what you're doing and make efforts from the very beginning to build your product in an accessible fashion
[1]https://www.wired.com/2015/09/whatsapp-serves-900-million-us...