How about three types? 1) Engineers who work on the external-facing side of the interface (possibly involving using many interfaces to build something with a u

How about three types? 1) Engineers who work on the external-facing side of the interface (possibly involving using many interfaces to build something with a user-facing interface, e.g. many app writers) 2) Engineers who work on the internal, engineer-only side of the interface (maximizing performance, optimizing at a low level, e.g. library writers) 3) Engineers who design systems by building interfaces at the correct points in the overall design that separate (1) from (2) (network engineering might fit here).