Hi there. I interviewed the creator of FastAPI (https://sourcesort.com/interview/sebastian-ramirez-fastapi) about his experience researching, designing and developing a Python API framework. I think it provides a lot of good insight into the work that goes into creating a successful open source product. FastAPI has grown pretty quickly (8k stars on GitHub) since it was released a little over a year ago and I think that is largely down to Sebastián's devotion to creating a great developer experience.
I hope there are some useful lessons here for other devs on here, and I welcome any feedback on the format/style of the interview.