See A Satellite Tonight is my most successful side project so far, with 5 million users since launch in 2019. It's been entirely a solo project, and I've used it as a proving ground for a bunch of tech that I wanted to learn. It took dozens of APIs and services to put together the experience I wanted:
In this post I'll describe how it all works. Frontend tech, satellite-related calculations, backend tech, plus a little about my motivations for building the site.