We are using JavaScript for our SaaS-Backend
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. ... 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.