Most of my work has been on proprietary codebases. Here are a few small projects that are publicly available.
simple_jsonapi is an easy-to-use and easy-to-understand library for building JSON:API documents in Ruby. I developed it after finding that the available JSON serialization libraries were either generic and difficult to use for JSON:API or overly integrated with the Rails framework.
A rather simplistic implementation of a diffusion-limited aggregate that I wrote as an exercise in learning TypeScript.
composite-logging is a Ruby gem that supports logging to multiple locations, customizable formatting, tagging, thread-safe silencing, and a simple configuration DSL. For a bit more history, see the blog post.