From https://stripe.com/about:<p>"Andreas has hacked on everything from packaging systems to graph databases in Common Lisp. He used to help Patrick and Saikat with their Lisp woes in #lisp back in the day."<p>Is that means that Stripe was completely build with Common Lisp?
I'm not a Stripe employee (or associated with them in any way), but from what I've gathered from Patrick, they're using mostly Ruby for their stuff. They have several Lisp hackers but I don't think they're actually using it on their site.