Cloud Pub/Sub

It is a message-oriented middleware to the cloud that is simple and provides scalability, flexibility, and reliability for streaming analytics and event-driven computing systems.

It provides many-to-many asynchronous messaging, decoupling senders and receivers. It allows secure and highly available communication between independently written applications. The following image shows the architecture of Cloud Pub/Sub:

When to use

The following table illustrates some of the use cases for Google Pub/Sub:

Balancing workloads in a network cluster	Efficiently distributing a large queue of tasks among multiple workers, like GCE
Implementing asynchronous workflows	An order processing application can place an order on a topic, from where it can be picked/processed by one or more worker
Distributing event notifications	A service sends notification on new user registration. Subscriber will receive the notification after registration completion.
Refreshing distributed caches	An application can publish...