tl;dr Go with what you know and are comfortable with. Any of those you mentioned could be used. Personally, I prefer a more hands off framework such as Express

tl;dr Go with what you know and are comfortable with. Any of those you mentioned could be used. Personally, I prefer a more hands off framework such as Express (Node.js) or Bottle (Python) compared to something like Rails. Where do you see Sinatra or Flask fall short? That may help us in answering your question.