I worked at Hotelicopter, which was a hotel meta-search engine written in Ruby on Rails. We were bought out by the six major hotel chains in the US and re-branded as Roomkey.com. To get us started, they agreed to push a lot of traffic at us. We knew from load testing that it would be very difficult, with our practically non-existent ops team, to scale Rails to handle 1000x our current load.

We knew we had to rewrite the system in a more scalable language, and we had to be live on a fixed date. This was late 2010, early 2011. Our CTO evaluated a number of languages and chose Clojure. A team of five or so devs was able to write the entire system in a few months and launch without problems. I don't think that would have been possible in a non-lisp language.

The Clojure learning curve was steep, especially since stack traces for anonymous functions in Clojure 1.1 often began with "nil pointer exception, no source file, line 0."

Once our dev team "got" Clojure, we were hooked. The verbosity of other languages started to look appalling. Clojure let us iterate quickly without sacrificing performance, which was suddenly a big issue.

Writing Lisp code permanently changed the way I think, and the way I code in other languages. I strongly prefer composing short, deterministic functions, which are testable and easy to reason about.

Roomkey became a victim of the pandemic, when hotel bookings declined sharply.

I'm just now starting to pick up Common Lisp, and it's a joy: the simplicity and consistency of the language, the REPL, the emacs integration. I also like that it compiles to native code. That's good for performance and for deployment, since it doesn't require the target machine to have a JVM.