Come with me on a journey through the realms of state machines, with the practical brilliance of Erlang’s gen_statem behaviour as our light beam. Building on state machines as a model to reimplement technical debt, we will traverse the intersection of gen_statem practical implementation and the theoretical foundations of state machines. Using real-world application examples, we will go over from the industry beast to the theoretical abyss, revealing the mathematical elegance inherent in state machines and its more powerful automata siblings. Bridging this gap, we will empower Erlang developers to architect solutions that go beyond conventional patterns, with concrete examples and plenty of code to read, providing the attendees with a comprehensive vision to harness the full potential of gen_statem.