MQTT vs Sparrow: What are the differences?
MQTT: A machine-to-machine Internet of Things connectivity protocol. It was designed as an extremely lightweight publish/subscribe messaging transport. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium; 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.
MQTT and Sparrow can be categorized as "Message Queue" tools.