A badly designed front-end can negatively affect your backend code. For example, a radio button can lead to cleaner code, only one callback for the whole option

A badly designed front-end can negatively affect your backend code. For example, a radio button can lead to cleaner code, only one callback for the whole option-set and one dispatch per each option. However, changing the radio to a checkbox will lead to some woolly code. Similarly, the introduction of an accurate progress-bar might require the introduction of threads to the backend, or force you to update a global variable, or even rewrite it as an stream-based algorithm. For CLI applications, independent utilities (a la git) might lead to cleaner code, but sometimes you want to pass more state between phases, and having a per-application shell, a la OpenSSL might be better since you can then implement variables and pass intermediate representations in memory, instead of disk files and sockets.