I worked at a business (in ruby) where the entire core logic of the app was a state machine, as an idea the thought was good, a state machine modeled order flows pretty well, but in practice it was very slow and the amount of side effects that had to be considered as the business grew just compounded this.

It got to the point where this state machine approach was a real bottleneck and though I left before it was resolved last I heard they had to put real engineering time in to move off of it.

Be very careful when deciding to go this route.