React native + Firebase will get you a demo very quickly, especially on the standard functionalities. Fake the others at first, and then you can decide how to i

React native + Firebase will get you a demo very quickly, especially on the standard functionalities. Fake the others at first, and then you can decide how to implement them with a custom api, e.g. on gcloud. Launch in less than 3mo if you can, you can always iterate down the road.