https://pickyskincare.com - a tool that lets you find skin care products based on the ingredients you want and don't want in it. The main use case is for finding cheaper versions of a product you already like, or one without things you're allergic or sensitive to.
It's written in elixir using Phoenix live views. There's almost no custom Javascript outside of what that framework gives. First load may take a while because it's the cheapest tier of fly.io and boot loads all known ingredients and products in to memory.