Dealing with change in event sourced applications, with Michiel Rook

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).

[@lucasterable]

The problem is not only in the versioning of events themselves, but also in the HANDLING thereof!

[@Jakub-yu2vy]

very nice talk !

[@damaddinm88]

Just great 🙂

[@AugustoRz]

Something I seen often on this talks is that the examples of 'evolving' an ES system are quite trivial (versioning, upcasting), but there are no examples of more complicated and real life scenarios in which events have to be merged or split. And an explanation of the tooling that this requires.
Also the tooling/developer experience with Axon is non-existant. Do you want to check what consumes an event? Tough luck, you have to search for methods that receive the event class (or super classes!!!) as a parameter.

[@JohnMcclaned]

Build it yourself, it's your competitive advantage. You only have to do it once.

[@jeffcrow1481]

About versioned event store - all (interested) read models after this operation should be updated according to the change in es or rebuild, the problem will appear for external third party systems which must be informed about the change.

[@jeffcrow1481]

Why just don't create new events wich will update iban format for every account? Concern about a big number of new events shouldn't be the problem for looking to workaround? at least for this scenario?

[@KhaledKimboo4]

33:40 what a horrible language, java should be illegal