Greg Young has some very interesting ideas surrounding explicit state transition models. The end result is a system that can be rewound and fast forwarded and

Greg Young has some very interesting ideas surrounding explicit state transition models. The end result is a system that can be rewound and fast forwarded and that doesn't use a database in a traditional way. In fact he recommends an in-memory current state, while past state snapshots and the complete history of state transitions written to disk. It is interesting how he started with a domain problem and the end result lead him to a NoSQL type system with a denormalized reporting database.