Jef Claes

Somewhere around a year ago, we started using GES in production as the primary data store of our new loyalty system. The system stores two types of data. External services push batches of dumb downed events to the loyalty system. For example: a user logged on, played a game or participated in a competition. These events are transient by nature. Once the loyalty system has processed them, they only need to be kept around for a few days. When these ingress events are processed, they go through a mini pipeline in which each event is assigned a specific weight, for then to be aggregated and translated to a command. This command awards a user with virtual currency to spend in the loyalty shop and a number of points contributing to a higher rank - unlocking more priviliges. The state machine that stores a user’s balance and points is backed by a stream which is stored indefinitely. Unless the user asks to be forgotten that is. As a rough estimate, for every 1000 ingress transient events, only 1 needs to be stored indefinitely as part of a state machine. ...

Late 2017, we set out to replace and upgrade our existing reporting and analytics infrastructure with something that would be a better fit for our workloads. Keeping costs and required maintenance at a minimum would be a nice plus, making for an easy sell. After a bit of research, it was obvious Amazon Redshift had the potential to tick all the right boxes. While steadily porting the most problematic workloads away from our existing infrastructure, I started writing an investigative article on the fundamental concepts of Amazon Redshift. I learned a lot studying each individual building block, allowing me to make some small, but impactful changes to our own setup along the way. ...

Another year, another 17 books, 6 shows and 3 movies consumed. Here’s this year’s highlights. Books The Zen and Art of Motor Cycle Maintenance The author is a tormented soul on a quest to define quality. You’re his passenger, driving shot gun on a CB77 Super Hawk, in for an exhausting intellectual journey through the high mountains of reasoning. You will often fear getting lost and feel slightly anxious that the driver might drive of a cliff any moment, but he won’t. Once you see the top of the mountain for the first time, you’ll be happy he doesn’t make it too easy on you, and you’ll be more appreciative of the road that took you there. ...

Before last week, the only certification exam I ever passed was the Microsoft .NET Framework Application Development Foundation certification. This was almost eight years ago. My manager back then thought getting certified was the best way for me to get a raise. It would be a win-win. I for one would learn something along the way, and the company would have less trouble keeping its Microsoft Gold partnership. As far as I remember, I spent a good six months reading, studying and memorizing this 794 pages thick book. Although the book did teach me a fair amount of solid .NET framework internals, most time was spent force feeding myself the ins and outs of framework API’s you only need once in a blue moon and should just Google for when needed. ...

Most EventStore client libraries allow you to subscribe to a stream by passing in a callback which is invoked when an event occurs (either a live or historic event). type Envelope = { Id : Int64 Event : Event Historic : bool } type EventOccurred = Envelope -> unit Let’s say we subscribe to a stream of a popular video service, and we want to project a read model that shows how many videos a viewer has watched. We don’t care about the bookmarked videos for now. ...

I’ve been wanting to share this experience for a while, but it took me a while to come up with a story and example I could use in a blog post. I help out during the weekends in a small family run magic shop. I’m the third generation working in the shop. My great-grandfather always hoped that his only son would follow in his footsteps as a carpenter. But at only eighteen years old, my grandfather said goodbye to the chisels and sawdust, and set out for the big city to chase his dream of becoming a world class magician. The first few years were tough, he was no Houdini. He would (hardly) get by performing at kid birthday parties, weddings and store openings. That’s how he met my late grandmother. She worked as a shop girl in one of the first malls that were built in the city, and happened to show up each time my grandfather performed in one of the stores. After getting married, having a baby (my dad) and saving every dime they earned, my grandfather was able to rent a hole in the wall and open up his own tiny magic shop - in that same mall. Once my dad finished school, he worked as a middle school teacher for a few years, giving up on that job to join his father in the family business. He loves to tell you how he can now still teach children, without the chore of grading their homework. I’ve been running around and helping out in the store since I could barely walk. I guess you can say that magic runs in our blood. ...

I’ve organized a few DDDBE meetups in the past, and always succeed in forgetting something. Either someone points it out well in advance, or I end up stressing last minute. This post partly serves as a checklist for myself, but it would be a welcome side effect to also see it encourage others to help out organizing future meetups. Organizing a meetup is not rocket science, having a list of what to take care of is a good start. ...

At work, we’ve all grown quite vigilant when it comes to customers trying to cheat the system. A necessary trait when working in a domain where money flows back and forth and customers are always trying to find an edge that will turn the tables. While most tend to leave this mindset at work, one colleague in particular, is always probing, trying to find cracks in the surface of everyday models. Years of practice have made him exceptionally good at it too. When you want more than a shallow review of your design, you go see him. ...

When people get paid to write software, we very often find some form of friction between the people that build the software and those that pay to have it built. The company I joined three years ago was no exception. When I joined, they had just launched three months ago, weren’t seeing any return on investment and prospects weren’t too bright either. I won’t lie, that first year was quite stressful. The business model sucked, the code was even worse. That first year, I wouldn’t have been too surprised if the whole team had been let go. In that situation, I could have played it safe, but to be fair, there was something quite exciting about actually having skin in the game and trying to make something out of nothing. ...

I’m keeping the tradition alive, sharing how much I’ve consumed over the last year highlighting the things that stood out. 18 books, 8 movies and 9 shows. Looks like I consumed more than other years, which probably also explains why I produced less after-hours. Books I finished the Dark Tower series after 3 years. Following Roland Deschain and his ka-tet throughout the 8 books has been an epic adventure. Finishing Harry Potter by the time I was 18, I had little hopes to be ever dragged into such a long and captivating tale ever again. The Stand, another epic by Stephen King is also high up on my list. I’ve seem to have taken a liking to stories that are set in a post-apocalyptic world, in which the antagonist is not necessarily a horde of zombies. ...