Dealing with change in event sourced applications

In software development, change is pretty much the only constant factor. In fact, embracing change is one of the twelve principles behind the Agile Manifesto. As time passes, our understanding of the domain we are working in evolves. We develop based on new requirements, (better) insights, opportunities, changes in the market or legislation, or other factors.

These inputs eventually all lead to modifications to our application, which can be very challenging to implement if the application uses event sourcing. Indeed, when applied very strictly, event sourcing can be quite resistant to change. And unfortunately, there’s not a lot of literature on this subject (yet).

In this talk, we’ll explore how to deal with projection updates, event versioning and the GDPR, and the tools offered by a popular framework (Axon).