For example, you remove an attribute from a class definition. Your existing objects get (lazily) updated to reflect that change, following a rule you even have control upon. You don’t have to restart a process and then re-create your objects. The same is true for Lisp web development. You can create a new route, compile it and try it live without restarting the server. You didn’t have to restart a process. It’s all very interactive with instant feedback! — Why Lisp?