If you use Java I'm assuming you are not using process. If so, I believe Phoenix is no worse than Java applications in terms of ease of use and scalability etc.

If you use Java I'm assuming you are not using process. If so, I believe Phoenix is no worse than Java applications in terms of ease of use and scalability etc. And it in terms of performance it indeed require some design experience on Erlang process. But it shouldn't be bad. After all WhatsApp and Discord have run on top of it with very few engineers to support massive customers before. I doubt online charging system could be more chatty.