Having worked in both frontend- and backend-focused teams, I learned that the best way to design the implementation of new features is at the fault lines of the architecture, the APIs.

Working API first means defining the contract at the API level as the starting point. These contracts are written in the Openapi specification, a well-established format that benefits both sides of the API. Using code generators for the client and server side code parts makes sure the data is always transferred in the correct shape.

Since APIs are often the lines along wich we split up teams, working API first is a great strategy to decouple them.