Uber app contains very similar functionality, namely real-time map view that needs to be able to render any part of the globe (or at least serviceable area), a location search engine, the ability to render drivers around you in real-time.
Just like Google Maps lets you select point A-B directions across cars, walking, public transit, Uber gives you multiple products to select (UberX, UberPOOL), and renders the path on the app accordingly.
The Uber app also does a lot of extra computation at the app side to solve some of the business problems that the OP mentioned in the thread. For example (from the Twitter thread):
> Without manual pickup location entry people’s location would just show up as whatever the GPS location was last received. This can be very inaccurate (especially in cities with tall buildings) and drivers would end up on the wrong block. This was a horrible customer experience.
Uber app also tries to resolve and render points-of-interest, so that you don't have to search for just an address as your destination, you can also search for "Dolores Park". That not only powers the search on the backend, it's also rendered on the frontend so that when the map tile for Dolores Park is rendered, the app knows to drop a tree-shaped icon on top of it labeled "Dolores Park". Uber has been using their own maps for a lot of this, and has an entire Maps org that does in-house map display, routing, and search.
And that's just the before-trip functionality. There's extra stuff that happens during the trip, including showing your current location, being able to share your trip with friends, real-time 911 calling for safety, etc etc.
And this is all just the similarities with Google Maps. Uber does extra stuff on top of that, including:
Onboarding flows for signup/signin, including the 3rd party identity services.
Payments: the app needs to support payment linking flows so that you can add and verify your credit card. Sometimes your credit card declines, and there's a whole arrears flow that needs to be built out to support that. And credit cards aren't the only way to pay for trips in Uber, you also have proprietary systems like Venmo, and PayPal that you can link. And on top of that, there are myriad such proprietary wallets all over the world that Uber has supported since at least 2015, including PayTM (in India) and Airtel Money (India and Africa), just to name a couple examples. And in most of the world outside of the US, you can pay for Uber trips with paper cash, and that's a whole flow on the frontend during onboarding / arrears settlement. This needs to all be packed into the same binary because you don't download a different version of the app when you go to a different country.
They also bundle UberEats into the app for some people, and there are probably hundreds of other random features that are prototyped and hidden behind feature flags, or variable experiences that are selectively rolled out in certain geographies. They all need to be packaged into the same binary for everyone.
Throw in other random product features like their Spotify integration, and it all adds up. Uber isn't just a dumb CRUD app.
You can also see the same in other comparable apps, Lyft's iOS app is 290 MB, Ola is 205.3 MB, Grab is 289.6 MB, GoJek is 236.2 MB, Yandex Go is 145.4 MB, etc etc.
EDIT: there's an even better written summary somewhere up-thread of the sheer amount of business complexity that needs to be baked into the app -> https://news.ycombinator.com/item?id=25376346
