Google Cloud Pub/Sub (docs) is designed to provide reliable, many-to-many,
asynchronous messaging between applications. Publisher applications can send
messages to a "topic" and other applications can subscribe to that topic to
receive the messages. By decoupling senders and receivers, Google Cloud Pub/Sub
allows developers to communicate between independently written applications.

WWW: https://github.com/googleapis/google-cloud-ruby/tree/master/google-cloud-pubsub