Ask HN: What real-world apps are based on less popular disciplines of CS?

It seems like HN can't get enough of AI/Machine Learning (with Robotics sort of lumped into those) and Crypto at the moment, but for those that aren't interested in solely those disciplines, what real-world applications are you seeing that are focused around other central disciplines of computer science? Such as:

* Architecture

* Performance

* Graphics/Computer Vision

* Networking

* Concurrent/Parallel/Distributed systems

* Databases

* Human-Computer Interaction/UX

* Scientific/computational science