I'm trying to draw up a schematic on paper, so this is it... 1) The app will essentially be the front-end. The user will only be using the app to make payments

I'm trying to draw up a schematic on paper, so this is it... 1) The app will essentially be the front-end. The user will only be using the app to make payments, view a map (with cars on the road), track their car, request / cancel a car, and provide feedback. So the heaviest usage would be from the server to the user and not the other way around. I'm not sure how much Google Maps uses up per minute and how much data is needed to push a car's new position to the phone. That would seem to me to be intensive though, especially over thousands of people. Edge cases would be 0 and 25 cars live on a map. Also, I currently have one droplet with DO. Am I supposed to have at least 3? (website, app, DB )