Event Sourcing (ES) is a software design that requires the persistence of events instead of results. In the Programming experience section of Chapter 1 , First Steps Toward Reactive Programming, we had the opportunity to understand how to persist data in a reactive way. Even though this is not mandatory using ES when programming reactive, this is the most natural way of dealing with data persistence from an observable sequence.
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Talking exhaustively about ES is outside the scope of this book. We will assume the reader already has some knowledge about ES. Otherwise, here are some details: ES: https://msdn.microsoft.com/en-us/library/jj591559.aspx CQRS with Event Sourcing: https://msdn.microsoft.com/en-us/library/jj591577.aspx Further reading: Microsoft .NET: Architecting Applications for the Enterprise, 2nd Edition, Microsoft.
By implementing the ES design instead of persisting results at specific dates, we persist data exactly as we receive it from an...