Mosquitto vs Sparrow: What are the differences?

What is Mosquitto? An open source message broker that implements the MQTT protocol. It is lightweight and is suitable for use on all devices from low power single board computers to full servers.. The MQTT protocol provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it suitable for Internet of Things messaging such as with low power sensors or mobile devices such as phones, embedded computers or microcontrollers.

What is 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.

Mosquitto and Sparrow can be categorized as "Message Queue" tools.