Bonton Connect

We actually did use Java to build our client app for a very long time, until one of us decided to try out Kotlin and was blown away by how elegant and productive the Kotlin language is.

We actually use both Mongo and SQL databases in production. Mongo excels in both speed and developer friendliness when it comes to geospatial data and queries on the geospatial data, but we also like ACID compliance hence most of our other data (except on-site logs) are stored in a SQL Database (MariaDB for now)

While Redux may be the industry defacto, our team's OO driven minds find it comfortable to reason about in MobX (mobx-state-tree to be exact). It's a much more magical and painless experience compared to Redux.

We actually initially wrote a lot of networking code in Kotlin but the complexities involved prompted us to try and compile NodeJS for Android and port over all the networking logic to Node and communicate with node over the Java Native Interface.

This turned out to be a great decision considering our battery usage fell by 40% and rate of development increased by a factor of 2.