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Introduction In the previous post we learned how to implement a sample ordering service using the Akka-DDD framework. The service exposed the Reservation Office responsible for preparing and confirming the reservation of products, that the client added to their shopping cart. We learned that an office is a command handling business entity whose sole responsibility […]

Introduction In this episode we will learn how to assemble a subsystem that encapsulates functionality of a sub-domain of an e-commerce enterprise. The subsystem will be built on top of the Akka platform following a CQRS/DDDD-based approach. We will use the Akka-DDD framework, as it already implements concepts discussed previously, such as Aggregate Root and […]

Introduction It has been a while since I wrote the last episode in my series: „The Reactive DDD with Akka”. In that time, in 2015, I managed to release the two new projects: Akka-DDD – project that contains reusable artifacts for building applications on top of the Akka platform, following CQRS/DDDD-based approach, ddd-leaven-akka-v2 – follow-up […]

Let’s continue our adventure with Akka and DDD (previous lesson). So far we have been concentrated on write/command side of the system. We have covered topics like command processing, event storage, sharding etc. but haven’t touched the other side of the system: the query side. Our goal of this lesson is to implement necessary infrastructure […]

Recap of lesson 1 In previous lesson we have managed to implement abstraction of event sourced Aggregate Root (AR) using akka-persistence and use it to develop concrete AR class representing Reservation process. We have shown that AR is message driven component that reacts on command messages. If command (i.e ReserveProduct) is accepted AR produces event […]

When comparing traditional and DDD/CQRS architectures (see my previous article) I said that the goal of DDD model is to decompose complex business domain into manageable pieces taking into account scalability and consistency requirements. What it means is that by bringing concepts like bounded contexts, transaction boundaries and event based communication DDD and CQRS are […]

Rich domain model that emerges from application of DDD techniques has many advantages over anemic model but is hard (or even impossible) to deliver when modeled entities need to be stored in relational database. The reason lays deeply in the mismatch between goals of DDD and ORM models. Without going into details, the main difference […]

O czym traktuje wpis: CQRS – Command Query Responsibility Segregation DDD – Domain Driven Design ES – Event Sourcing Koncepcja CQRS Podział systemu na dwa obszary: przetwarzanie transakcji obsługa zapytań (widoki) Koncepcja CQRS Architektura systemu, która wyłania się w wyniku zastosowania takiej separacji, jest zasadniczo różna względem typowych architektur bazujących na jednym modelu danych i […]

CQRS (Command Query Responsibility Segregation) is a new approach towards building scalable and distributed systems that is based on simple pattern know as Command Query Separation (CQS). In short, you should design your system in a way that it either processes a command or serves response to a query. CQRS in its core is quite […]