This is the first article in a series dedicated to FSM usage in distributed system architecture. We will talk about domains, transactions, and sagas. But let’s start with the basics. Finite-State Machine When we think about the finite-state machine, we probably imagine some computer science-related entities, math, and diagrams like that: Besides scientific language, a finite-state machine is a final set of states and the transitions between them. When it comes to real engineering, states are a set of consistent states in which the model can be.