The official AWS X-Ray Recorder SDK for Ruby
Reactive Extensions for the JVM
Prometheus instrumentation library for JVM applications
Guard is a command line tool to easily handle events on file system
Modern concurrency tools including agents, futures, promises, etc.
Ruby ODM framework for MongoDB
Ruby library for creating background jobs and processing them
Marathon supports testing of Java/Swing and Java/Fx applications.
An API for asynchronous programming with observable streams