<bq href="https://www.hyrumslaw.com/" author="Hyrum Wright" source="">“The Law of Implicit Interfaces”: <b>Given enough use, there is no such thing as a private implementation. That is, if an interface has enough consumers, they will collectively depend on every aspect of the implementation, intentionally or not.</b> This effect serves to constrain changes to the implementation, which must now conform to both the explicitly documented interface, as well as the implicit interface captured by usage. We often refer to this phenomenon as "bug-for-bug compatibility."</bq> <bq><b>For example, an interface may make no guarantees about performance, yet consumers often come to expect a certain level of performance from its implementation.</b> Those expectations become part of the implicit interface to a system, and changes to the system must maintain these performance characteristics to continue functioning for its consumers.</bq> <img src="{att_link}spaghetti_apis.webp" href="{att_link}spaghetti_apis.webp" align="none" caption="Spaghetti APIs" scale="75%">