Kestrel vs Sparrow: What are the differences?
Kestrel: Simple, distributed message queue system. Kestrel is based on Blaine Cook's "starling" simple, distributed message queue, with added features and bulletproofing, as well as the scalability offered by actors and the JVM; Sparrow: A really fast lightweight queue written in Ruby that speaks memcache. Sparrow keeps messages in memory, but persists them to disk, using Sqlite, when the queue is shutdown.
Kestrel and Sparrow can be primarily classified as "Message Queue" tools.
Kestrel is an open source tool with 2.8K GitHub stars and 326 GitHub forks. Here's a link to Kestrel's open source repository on GitHub.