I was fortunate enough to attend the GOTO Conference 2017 in Chicago. Martin Fowler who was the keynote speaker on Monday talked about Event Driven Architecture. From the 4 different system he mentioned; event sourcing seemed to be the coolest.
So here is a very basic example i could think of that works?
[Customer] - a single enttiy that represent a state
[AccountSystem] - Which is hidden inside out EventStore and called from there
[EventStore] - is the one that calls the events and delegates transaction call to the AccountSystem
[TransactionEventBook] - subscribe to the event inside the EventStore and stores all the Transction
[BookReplay] - replays events in the book: all, n amount, or filtered by CustomerId;