I run a company called TalkJS (
https://talkjs.com). We're a toolbox that lets our customers build a proper chat feature in hours instead of months.
This means lots of API design and I love to do API design. I get a deep sense of flow and purpose when dreaming up a tool (an SDK, a library, a language, a set functions or data types; whatever) that lets other programmers do a wide variety of things.
Admittedly the other half of my job is business & marketing related. I like it too, especially since "sales" in our case mostly means talking to other programmers, and so does "management". But not as deeply as the code work.
It also helps that since we're a remote-first company I can choose from where I work and I stop when I notice I'm too stuck or "my brain is full". We don't really do the typical startup-burnout-marathon.
