For our SaaS-product Botium Box - a full functional and non-functional testing infrastructure for chatbot - we decided to go for Node.js in the backend.

There are lots of controversial arguments about programming language in general, and using a non-type-safe, dynamic scripting language like Javascript for server-side development. In our company we have a strict no-bullshitting-policy, so we didn't go very deep into the more philosophical aspect of selecting a programming language.

After all, it came down to a decision Python vs Javascript. While Python is by far the most mature language for machine learning projects, the one single argument why we decided for Node.js was that in our small developer team (4 people) everyone is a full-stack-developer, and it will ultimately safe time to develop client and server in the same programming language.

P.S. For some machine-learning-centric components of our SaaS-backend we still decided to go for some micro-services developer in Python.