Oh cool! so from the server you stop the image that's running on the server, then restart the CCL image, and then load in the source (like starting a repl on the server and doing a "load ./start-file.lisp")? (ps sorry for the rookie questions am quite new to this and very interested).
Yes, exactly. (And no worries about rookie questions. That's how people become non-rookies.)
In my case, I run the REPL using screen so I can go back to it for debugging if I need to. But you can also run "headless", without a REPL at all if you want.
Yep, pretty much. I've only ever dealt with low-load applications so there was no load balancer. You just put the Lisp server in a state where it refuses new connections (serves up a "temporarily down for mx" page, or reconfigure the ngingx front end to do that), wait for existing connections to finish, and then restart. It's no different from any other server.