Common Lisp can be compiled one function at a time, and functions belong to packages, which are pretty much key-value databases you can modify, where keys are s

Common Lisp can be compiled one function at a time, and functions belong to packages, which are pretty much key-value databases you can modify, where keys are strings (name of the function) and the values are the functions themselves. So if there is something wrong with some function, I just update the value in the "database" and all callers will call the newly defined function from now on. Nothing magical really. This workflow is supported by the CL IDEs such as SLIME.