Last week of January, the first DDD Europe conference took place in Brussels, Belgium. Looking at the schedule, you’ll find that the who-is-who of the community came and delivered their talks.

There are already some very detailed reports of the conference, so I’ll promise to keep it short.

Cyrille on “Heuristics from the trenches”

Cyrille Martraire gave an excellent presentation about his way of exploring a domain together with domain experts. A crucial point he made was, that it’s hard for someone, whose expertise is built upon a legacy system, to escape its intricacies and look at the domain from a distance.

This is why I love to sit down together with new interns here at vaamo and explore their experience with our application and how they think it could be improved. They usually provide me with excellent insights into our business processes and what we can further improve.

Also, one has to really honour the energy he brought to the stage at 9.30 AM. Make sure to watch his talk once the videos are up, it’s hilarious and enlightening at the same time.

Martin Kleppmann on “Event sourcing and stream processing at scale”

In his talk, Martin Kleppmann, who formerly worked at LinkedIn, tried to bridge the gap between Event Sourcing and Stream Processing. Personally, I found this talk really interesting, as the similarity of both techniques is intriguing, yet they solve so different problems.

At LinkedIn, they make heavy use of Apache Kafka as their event store mechanism.

Out of curiosity, I ported our database layer to Kafka last year, just to find that it didn’t provide us with any benefits over our current architecture.

Martin on the other hand, presented their architecture, which basically revolves around enriching very raw events and storing them back into their Kafka storage. This is how they get from User visited website to User visited Profile and eventually to Users who viewed your profile.

Ultimately, stream processing solves a different problem than event sourcing: While LinkedIn handles a vast amount of events and has to scale with their visitors (on average, LinkedIn processes 18 million events per second), DDD (at least at our scale) is all about communicating intent and context in your code and maintaining a fitting domain model.

You can find his slides on his website.

Vaughn Vernon on the “Odds and Ends”

This is actually a talk I only got to see when Vaughn visited Berlin the week after DDD Europe for his workshop. He kindly repeated the talk at the newly founded @DDDBER Meetup.

His talk mainly revolved around our industry, and about the importance of IT becoming a profit center, whereas it’s often perceived as a cost center right now. He hit home when he stated something so obvious that we rarely talk about it, yet it happens to us so often:

And of course, it’s obvious that the one developer dedicated to runtime support is wasting their time with fixing errors, but you can really only see the effects once you’ve got rid of these chores and see them and their velocity once they are back to developing real features for your application.

Also, Vaughn presented (we maybe got a little sneak preview, who knows?) the Green Book, which will come out this spring, which I’m really looking forward to.

Further reading: Michael Feathers’ Essay “Symbiosis - A Provocation About Organizations”

The unconference

The one thing I enjoyed most about the conference was - without a doubt - it’s unconference flair. Whether you ran into a speaker in the Motel Lobby at 1 AM in the morning, or took the chance to do some domain modeling or Event Storming with Eric Evans and others in the unconference “Room” at the conference. It was really an engaging atmosphere, perfect for a conference that was born out of a community in the first place.

A great example for this was when Alberto Brandolini started his workshop on Event Storming: The room was already bursting with people, but next thing you know, Mathias Verraes started another Event Storming workshop in the lobby. Fast-forward 30 minutes later, the whole venue was filled with people putting up Post-Its on Walls, exploring Domains all while learning the technique.

To sum it up

TL;DR: It was awesome! It was truly a pleasure to meet old friends and make new ones, all while enjoying a well organized community conference.

Kudos to the organizers and all those who shared their reports and some special thanks to Michel Grootjans, who took some really awesome visual notes.