GOOD INTERFACES MAKE GOOD NEIGHBORS

Summary from the TLDR Founders newsletter

Good interfaces allow independent systems to work together without knowing everything about one another. Collaboration problems between teams are often interface problems rather than relationship problems. A good interface makes it obvious who owns what, what they are working on, and how new requests are evaluated. When those things aren't clear, even well-intentioned people end up wasting energy on disagreements and reverse-engineering decisions.