Events are at the heart of a CQRS Event Sourced system. Which is why changing or upgrading them can be problematic. In this post I’m going to cover a few principles to bear in mind, which should help you avoid hitting the rocks. Before I dive into ‘how to upgrade CQRS events’ I’m going to […]
The nice thing about programming is that everything is black and white. Wrong! When designing new features, we all go through a process of discovering requirements. If you are a good developer, you will start to ask questions and probe deeper to find the edge cases. Why? Because you know the edge cases can often […]
Ok, so you have two event sourced aggregate roots. You need to call a method in one from the other. How do you do it? If you find your self asking this question, don’t worry, your not alone. It comes up a lot. The short answer – it suggests there could be something wrong with […]
If you’ve been developing for any length of time you’ve probably had to create an audit log. Here’s the question though, are any of these logs, a 100% provable audit of all changes in the system? I’m guessing not. With event sourcing, a 100% provable event log just happens to be a handy by product. So […]
When starting out with CQRS, designing the ‘events’ is not always obvious or easy. The more experienced you are, the more likely your habits will lead you astray. This post will help you spot the problems early and stay on the right track.
One of the most liberating things about the CQRS ES way, is the simplicity of the read side. However, if you are new to CQRS you may have wondered how it works. How for example, would it work for a classic master details view? You are not alone, in fact, I am writing this post […]
Imagine if it was possible, when faced with a potential concurrency issue to programmatically check if any previous ‘events’ actually conflict with the current action being requested. With a CQRS Event Sourced application, it is possible to significantly reduce the problems of concurrency and in the remainder of this article I will show you how.
I had an ‘Ah ha!’ moment just over a year ago when I attended a Greg Young’s CQRS and Event sourcing course with skillsmatter. The ‘Ah ha’ wasn’t about CQRS, or even Event sourcing, it was about how Greg structured his code to work with messages. This approach can have far reaching effects on your software, making […]