You can troll through the job postings of most of these companies and learn about their org structures and tech stacks. When I looked almost nothing is public other than older documentaries. Nanex had some neat wiring diagrams and a few videos clips if you google them. Don't get too excited you're not going to learn about some super secret strategy or anything.

This book was good https://www.amazon.ca/Advances-Financial-Machine-Learning-Ma... in that is sort of explains at a high level how you'd build a company to look at something like this (think it was one of the last chapters). You'll need extremely deep/skilled hardware/networking groups, data acquisitions (think packet capture to data) folks, people to clean and maintenance massive the data repos, internal tool teams, quantitative analysts, traders, management/admin, etc. At this level just getting the fiber to each exchange likely costs many many millions. When you go and look through those job postings you can sort of slot these into your mental model of this flow and start to see how it might be put together.

That book is good but if you are new to the topic it will be almost unreadable. At least it was for me. I had to read it 3-4 times over the years and still find new things as my knowledge grows.

I don't know if rentec is a HFT firm or what strategies they use but this was a really good interview with one of the founders https://www.youtube.com/watch?v=QNznD9hMEh0.