Publish-subscribe (also known as Pub-Sub) is a communication or messaging pattern used in distributed systems, where messages are transported from senders (publishers) to receivers (subscribers) in a de-coupled manner such that they are not aware of each other. Instead, the sender categorizes published messages into channels and subscribers express interest in one or more channels. A message broker facilitates the transfer of messages between the publishers and subscribers based on the channel names or patterns.
Pub-sub pattern is well suited for highly scaled up, distributed and dynamic applications deployed over the Internet. It allows asynchronous communication between messaging endpoints, enabling loose coupling and improved responsiveness.
Pub-sub messaging is commonly employed in various scenarios, including event-driven architectures, real-time data processing, message queuing systems, and distributed systems where loose coupling and scalability are required. Apache Kafka is a well known implementation of Pub-Sub pattern. This pattern is also adopted in some of the standardized protocols such as MQTT (Message Queuing Telemetry Transport)) used in Internet of Things systems.