If you are looking for a list of my current and former employers, please visit my LinkedIn and Xing profiles. This page is more about what shaped me in a professional sense.

BASIC 1979(?) My first contact with programming was theoretical: Inspired by stories about computers, I learned BASIC purely from a book. I had a school mate with a Commodore PET but he never bothered to type in my lengthy code. I wrote programs on paper that would never be typed into the real thing to show their flaws. I devoured all the books I could gather about programming, to the point where the bibliothecaries of the surprisingly well-equipped public library of my home town would not let me hog any more.
Sinclair ZX811 1982 My first real and very own computer: A Sinclair ZX81 was found under the Christmas tree that year. Finally, those daydreams could become a reality, at least the part of them that fit into its RAM of 1 KB (about 850 bytes free). It certainly taught me being economical but much more than that: The excitement of programming!
TU dortmund 1988–1999 Studying Information Science at the University of Dortmund, Germany, enlightened my programming. I learned new concepts like functional programming (with Scheme), meta programming, the role of syntactic sugar and much more. To this day I believe that a solid knowledge of the foundation of the craft does inform a good programmer and IT architect. I thank the professors, staff, and co-students that introduced me to it and shared my passion. Oh, and I met the Internet. Hey, Internet!
Smalltalk 1990 Object-oriented programming was wild and strange new concept I had read about in German computer magazing c’t. When I saw a posting for an out-of-curriculum course on Smalltalk-80, I went in full in. A few weeks later I began working for Georg Heeg, a German pioneer in the field. Truly learning object-orientation from the ground up definitely gave me a head start years later when those odd new (and rather unrelated) languages called Java and JavaScript claimed the label for themselves.
Kent Beck: Extreme Programming Explained 1998 When Extreme Programming pioneer Kent Beck joined the company I was working for, Daedalos, I got exposed to the ideas of Extreme Programming and the methods that what would later be called “Agile.” I did get to pre-read a draft of his book but more than that, his always friendly attitude and his reluctance to compromise his ideas thoroughly impressed me. He gave me back programming how it used to be before bureaucrats and pea-counters had turned it into software accounting. Be thorough, apply engineering discipline, and achieve results.
Sushi variants2 1998–2002, 2008–2012 “The more things change, the more they remain the same.” Working as a consultant certainly showed me the truth of that quote: Projects, clients, teams, fields and topics, cultures, ecosystems, everything is different in every new project. And yet, there are similarities, recurring patterns. If anyone asked me for advice for a young professional in the IT field, it would be this: Be an IT consultant for a while. It will give you an edge by knowing how else you can do that thing, or how it worked out when they tried that.
Architecture3 1999 Architecture. Some seem to think that there is a contradiction between the discipline of IT architecture and “agile” methods. I beg to differ. Being an architect means to be a master of the craft who knows what will or will not stand, a visionary who can see things how they can be rather than how they are of old, and a communicator who can explain and inspire a crowd who will create a new reality. Sounds lofty? Well, certainly it is more fun than being a software accountant or a member of the standards enforcement committee. Working in large organizations either as an external consultant or a proper employee has taught me one thing at the least: IT systems decay into needless complexity and rut. The time of the architect is the future, and I, for one, embrace change.
DevOps4 2013 DevOps, to me, means applying the principles of software development to operations, and vice versa. One of my first jobs as a student was pre-sales and post-sales technical support for a relatively complex software product. I do believe that learning about the reality of operations problems arising from careless coding helps a long way convincing developers to code defensively and flexibly. But it works the other way around, too. Configuration as code, version management on configurations, automated deployment, resilient platforms, and full-stack monitoring are advances that are moving IT out of the corner of the unreliable and arcane into true mainstream. And it is so much cheaper too. (And more fun.)
Cloud 2014 Cloud platforms and cloud computing first truly appeared on my radar when Fiducia, then my employer, tried to optimize deployments and operations base on OpenStack and similar technologies. The real potential, however, only occured to me with the advent of Docker for container isolation, CloudFoundry for hassle-free deployment, and later Kubernetes, which is currently the gold standard for operating applications in a resilient, DevOp-sy way. At Allianz, we built an internal cloud platform (“public” cloud was a taboo word back then) which by now has evolved into a hybrid cloud setup, and it taught me a lot about how to introduce the concept to a large and complicated enterprise.
Machine Learning 1996(?) or 2020 Machine learning as well as evolutionary algorithms, recently reborn as adversarial networks, have always fascinated me since I read about the original Perceptron back when I was a child. The idea of mimicking actual learning in a computer rather than programming it seems to good to miss. My long friend Christoph Friedrich got the chance to work on these things professionally back even before the (second) AI Winter, while I was pursuing different roads. Now of course we have the powerful GPUs and the cloud platforms necessary to create immense models such as current generation of transformers like GPT-3. Maybe I am late to the party but fiddeling with Keras, hyper-tuning another dropout layer seems just as exciting as learning BASIC. Besides the tinkering, I see my role as an architect as being able to glimpse where these newly powers can be applied. (And yes, the sociological implications are enormous. All the more a job for an IT architect, among other disciplines.)
The Future tbd  

What I have provided here is of course only a small selection of my professional influences but I don’t want to bore you more than I probably already have. I have glossed over many points and I am sure I have missed some crucial ones but it is late, and tomorrow is another day. Perhaps I will come back to this page and amend it.

Picture attributions

I added the attributions with care and all the pictures shown here are my own or covered by CC-BY-SA. If I missed one, please do get in touch and I will certainly add it.

  1. By © Bill Bertram, 2006 - Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=500910 

  2. https://de.wikipedia.org/wiki/Sushi#/media/Datei:Sushi_variants.jpg 

  3. https://en.wikipedia.org/wiki/Architecture#/media/File:View_of_Santa_Maria_del_Fiore_in_Florence.jpg 

  4. By MarianSigler - Self-drawn using Inkscape and gedit, Public Domain, https://commons.wikimedia.org/w/index.php?curid=782781