What developers mean when they say "Legacy Code"

🎵 The song for this post is Scatman, by Scatman John.

In 2014, I built two Android apps for a 5-person startup in about two and a half months. In part because of lessons learned from the iOS app, was able to architect it such that it had some features iOS didn't. When the CEO asked the CTO if it was possible to port some of the features back into iOS, the CTO said

This is a companion discussion topic for the original entry at https://morepablo.com/2018/03/legacy-code.html