NodeJS application alongside GravCMS

Perhaps this questions is for the creators of Grav. Is it possible to have a NodeJS instance running alongside GravCMS website? The reason I am asking is because I would like to use BrainTree's API for payments. However, I am not great with PHP and would like to use NodeJS for handling payments. Is it possible to do and what is best way to go about it?

While you can do anything you want, I'd not mix and match completely different technologies. You can however create any Node.js app and offer an API that your Grav site uses, but there's no "guide" for this, as pretty advanced topic.