Not Lisp, but for those interested in editing programs that are running in production:

I read some Erlang article saying that hot swapping is not actually very useful in production because of some reasons, and instead a blue-green deployment is preferred. Can't find the link atm. This was close: https://learnyousomeerlang.com/relups

Compare to this comment: https://news.ycombinator.com/item?id=42405168 Hot swaps for small patches and bugfixes, and hard restarts for changing data structures and supervisor tree.