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The product I have been working on most for the past decade is Passenger: a web server and application server. Designed to be fast, robust and lightweight, it works as a reverse proxy and process manager in one. It is meant to take a lot of complexity out of deploying and administering web apps, as well as providing security, monitoring and management features transparently to apps. It's being used by high-profile companies such as Apple, Pixar, New York Times, AirBnB, Juniper etc as well as over 650.000 websites.
A Ruby gem which provides a way to specify default values for ActiveRecord models.
A system for building "portable" binaries for Linux: binaries that work on pretty much any Linux distribution. This works by providing an easy-to-use compilation environment with an old glibc version.
Supplies self-contained, "portable" Ruby binaries: Ruby binaries that can run on any Linux distribution and any macOS machine. This allows Ruby app developers to bundle these binaries with their Ruby app, so that they can distribute a single package to end users, without needing end users to first install Ruby or gems.
A special Docker base image designed to solve the PID 1 zombie reaping problem as well as helps you avoid various pitfalls in Docker usage. Many issues have since been addressed in Docker itself as well as the wider ecosystem. For quite a while this was the most popular third-party image on the Docker hub.