Architecture & practice·Design, structure and tradeoffs
the new feature was two things you already had, wired together, and nothing new was written.
Composability
The property that small pieces can be combined into larger ones without special cases. Composable parts have uniform inputs and outputs and no hidden state, which is what lets them be assembled in orders nobody anticipated. It is worth naming in a review because it is the difference between a system that grows by adding a piece and one that grows by editing the middle of everything that exists.