Isn't that part of Paul Graham's startup lore? They were running lisp web servers for their ecommerce store and while a customer was on the phone with an issue, they would patch the server live and ask the customer to reload. Customers would hang up convinced it was their personal glitch.

The tool uses a Forth-like language with immutable data structures and persistent memory snapshots. It also uses Clojure style meta-data and compile-time meta-programming. I have no luck convincing people that a language without curly brackets is useful.