A message queueing service is a message-oriented middleware or MOM deployed in a compute cloud using software as a service model. Service subscribers access queues and or topics to exchange data using point-to-point or publish and subscribe patterns. It's important to differentiate between event-driven and message-driven (aka queue driven) services: Event-driven services (e.g. AWS SNS) are decoupled from their consumers. Whereas queue / message driven services (e.g. AWS SQS) are coupled with their consumers. Message queues can be a good buffer to handle spiky workloads but they have a finite capacity. According to Gregor Hohpe, message queues require proper mechanisms (aka flow controls) to avoid filling the queue beyond its manageable capacity and to keep the system stable.

Goals

A message queueing service aims to eliminate the traditional overhead associated with operating in-house messaging infrastructures. These operating overheads include: Besides reducing cost, a message queueing service seeks to simplify access to messaging resources and therefore facilitate integration efforts within organizations and between them.

Benefits

A message queueing service also creates new value by providing reduced costs, enhanced performance and reliability. In order to provide those benefits, a message queueing service leverages cloud computing resources such as storage, network, memory and processing capacity. By using virtually unlimited cloud computing resources, a message queueing service provides an internet scale messaging platform.

Accessibility

A message queueing service is accessible through a variety of protocols such as Java Message Service, AMQP, REST-style APIs and web services.

Usage Examples

Vendors

IBM MQ offers a managed service that can be used on IBM Cloud and Amazon Web Services.