In my experience, the kinds of use cases for this level of optimization tend to be in fields where computers are used as actual computing devices. So think phy

In my experience, the kinds of use cases for this level of optimization tend to be in fields where computers are used as actual computing devices. So think physics, biology, etc. I'd guess most jobs in the HPC space would allow you to get pretty close to this kind of work in practice, although your job title might still just be 'software engineer' or whatever. Located in .nl, the oil and gas industry surely has some work that benefits from these kinds of optimizations. ASML probably does enough simulation as well. I'd guess there are probably a handful of financial firms operating on these time scales. Outside of those, the various universities will have groups in this space. I doubt that's an inclusive list, just some areas where I'd expect to find heavily optimized code for specific hardware.