Ask HN: Industries to Work with Algorithms?

Hey there - I am a Sr Software Engineer, working right now at a fintech, but most of my work for the past years have been working with APIs. Connecting to 3rd parties API and exposing our own API. So most of the work is implementing business logic in an API, though taking care of security, and a lot of boring (at least for me, now) stuff.

I always liked algorithms (especially when I studied them back in college), and after a talk with a friend who works with trading algorithms I realized I loved to pivot to work on a position that would allow me to design or at least improve algorithms. I want to do more of a work where I care more about the algorithm and its output, more than DB idnexes or stuff like that.

I would like to know which industries would offer that kind of positions (I'd guess industries related to trading stock, or localization/maps, for example), but I am sure I am missing something. Also, if someone knows, I guess that going into a position like that would mean I should start as a junior since it's a different kind of position?

Thanks!