Yesterday I took 45 minutes to watch Alistair Cockburn’s presentation on Hexagonal Architecture—the model he proposed decades ago.
It still holds up.
The idea is simple but powerful: create a strong boundary around your application logic. All interactions with the outside world—UI, DBs, APIs—go through ports. These ports are interfaces defined by the application, not imposed from the outside.
Cockburn compares this to a chip’s pinout. The application is the chip. It defines how things should connect. The rest must conform.
Most devs easily grasp driving ports (the app exposing APIs), but driven ports (external services implementing interfaces defined by the app) are less intuitive—and often neglected.
I haven’t applied this model to the letter, but I do apply its principles often. Clean boundaries, clear direction of dependencies, and a focus on isolating logic from infrastructure.
If you’re designing applications meant to evolve and grow, this is a model worth exploring.