Comment by ahartmetz

I find engineering-type stuff (kernels and hypervisors, programming languages, databases, concurrency, computer graphics, even proof assistants, deep learning now obviously, ...) most important since my impression of many German CS professors is that they would prefer to be mathematicians. There's a ton of interesting theory to be found in sufficiently advanced engineering, but you don't get any of that if you refuse to touch it. IMO, too little engineering is the main disease of German computer science.