RxAndroid VS OkHttp

Since you mentioned java, there is RxJava and RxAndroid. Google general recommendation now is to use kotlin coroutines if you're considering writing your app with that.

RxAndroid

Well, as mentioned in the RxAndroid's Readme, it's only Android extensions to RxJava. It makes it easy to subscribe or observe on the main thread or a specific looper. So just focusing on learning RxJava should be enough. You can find many resources for that, here is a compilation: http://reactivex.io/tutorials.html

Project: RxAndroid (Android specific bindings for RxJava) Copyright (c) 2015 The RxAndroid authors. License (Apache License Version 2.0) https://github.com/ReactiveX/RxAndroid/blob/master/LICENSE

We will use Square’s Mock Webserver to spin up a mock server which we can use to simulate real api's request to the get coffee endpoint.

OkHttp Documentation

mockwebserver -> https://github.com/square/okhttp/tree/master/mockwebserver

I searched in the OkHttp GitHub project for an advice on which values may be suitable for Android apps nowadays but found no answers (only this old issue which does not help). Since we share a single OkHttp client Singleton for all our retrofit APIs and even Coil, I wonder if the default 5 maxRequestsPerHost is really enough.

You can technically add a Content-Length header for each part. It's not forbidden by the RFC, but nor is it common. It caused [problems](https://github.com/square/okhttp/issues/2138) for OkHttp, and they eventually removed it. Might be fine for internal-only use, though.

Boundaries are a lot like UUIDs, and rely on the same logic. When generating random data, once you have enough bits, the odds are against that sequence of bits ever having been generated before in the universe.

Lets be specific. This is the gradle build file for Squares okhttp client library. How exactly would your bld tool "predict" or "help" with all the parameters needed? There is no need to be defensive. Replace those large build files with your own, show where your approach is better and then understanding will lead to better solutions.

And adding to that: The asynchttpclient library is just a thin wrapper around OkHttp3, so it might be easier to just go with that instead: https://square.github.io/okhttp/

Retrofit in combination with OkHttp for fetching data from server (which hopefully already exists)

OkHttp