Projection
The article discusses the development of a Read Model for a Bounded Context, which is a separate persistence store optimized for reading data. Data is inserted into the Read Model by using Event Handlers, which listen to events emitted from the Write Model after changes in Aggregate state. Nick implements a Bus to transport Commands and Events to appropriate Handlers. The article includes discussing how the Read Model can be made consistent with the Write Model.
ACK/NACK for Commands with CQRS
How to signify acknowledgement, or negative-acknowledgement, of Commands when applying CQRS.
Making your Application stable with Outbox Pattern
Whenever we send asynchronous messages and modify state in database within same action, we put ourselves at risk. The risk come from the possibility that state will be persisted and message will fail...
Real-Time Personalisation of Search Results with Auto Trader's Customer Data Platform
Engineers from Auto Trader explain how they use User behaviour to improve the quality of search results for customers. An interesting article exploring events, relays, derived data projections, Customer Data Platform and API gateways.
The Dynamic Duo: Event Sourcing and CQRS
A quick and simple overview of what CQRS and Event Sourcing is.
The Repository Pattern
What are Repositories? Why should you treat them as collections? How should you interact with them, and should they create your entities? Shawn covers many of these topics to provide a solid introduction to the Repository pattern.
Apache Kafka is not for Event Sourcing
Apache Kafka is a cool product, but if you are thinking about using it for event sourcing Jesper Hammarbäck thinks you should think again.
Can command return a value?
In this article, Oskar takes us through his thought process and provides his answer to one of the most-asked questions regarding CQRS: can a Command return a value?
CQRS + Event Sourcing - Step by Step
A step-by-step overview of cqrs and event sourcing focusing on the flow from Command through to Read Model.
Aggregate Root - How to Build One for CQRS and Event Sourcing
A quick step-by-step guide to building your own Aggregate Root for CQRS and Event Sourcing. With example C# code.
Pattern: Command Query Responsibility Segregation (CQRS)
Define a queryable replica that is kept up to date by subscribing to events published by the services that own the data.
CQRS
CQRS (Command Query Responsibility Segregation) is the notion that you can use a different model to update information than the model you use to read information
Clarified CQRS
After listening how the community has interpreted Command-Query Responsibility Segregation I think that the time has come for some clarification. Some have been tying it together to Event Sourcing. Most have been overlaying their previous layered architecture assumptions on it. Here I hope to identify CQRS itself, and describe in which places it can connect to other patterns.
Build a CQRS event store with Amazon DynamoDB
The command query responsibility segregation (CQRS) pattern, derived from the principle of command-query separation, has been popularized by the domain-driven design community. CQRS architectures that use event sourcing save generated events in an append-only log called an event store. By using event sourcing, you can, among other benefits: Design applications to update a database and [...]
Accidental Intent Cancelling
In this article, I introduce a form of Accidental Complexity I've been referring to as Accidental Intent Cancelling.
Pattern: Command Query Responsibility Segregation (CQRS)
microservices.ioDefine a queryable replica that is kept up to date by subscribing to events published by the services that own the data.