We have decided to start out using Erlang & Cowboy for this project. This is a naive decision based on some personal bias ideas but judging by the company that the language keeps we can't really go wrong!
We are using cowboy for the main monolith web solution but satellite REST apis will also be using cowboy.
Other Erlang tools we are shooting for are erlydtl as the main templating engine. This makes sense as I come from a Python / Django background & this templating engine is 1 to 1 port. I also decided on using pgo as the main postgres driver as it has support from an established org - Process One.
I have written my own migration library in Erlang which i may open source in the future.
So that's all for now. As & when I employ more Erlang functionality I will come back here with updates.
Bye for now!