How to implement transaction management in a hexagonal microservice? How to keep the isolation of the application layer and the database adapter? In this article I will share my experience in solving this problem.

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. Normally the set is not huge - having an FSM of a hundred states will cause really complex code. In my experience, it is something between three for the simplest models and 20-30 for most complex ones.