EventMachine

Implements the Reactor pattern for efficient I/O handling, similar to Node.js and Netty, enabling thousands of concurrent connections without threading overhead.

Has been stable since the early 2000s, used in production systems like Thin and Goliath, ensuring reliability for critical applications.

Abstracts away low-level threading complexities, allowing developers to focus on application logic with event-driven callbacks.

Runs on Ruby 2.0+, JRuby, and supports Windows, Linux, macOS, and BSD, making it versatile across different environments.