Explain the working principle of a push broker and its role in message exchange systems.

Push broker is a component in messaging systems responsible for delivering messages from the sender (publisher) to the recipients (subscribers) in push mode, meaning it initiates message sending without a request from the recipient.

Working principle:

• The sender publishes a message to the broker.
• The broker stores or immediately forwards the message to subscribers who are subscribed to the relevant topic or channel.
• Recipients receive messages automatically as soon as they appear.

Role in messaging systems:

• Ensures asynchronous communication between components.
• Allows system scaling by offloading senders and receivers.
• Simplifies the implementation of event-driven architecture.

Example: In a notification system, a push broker delivers messages about new events to client devices without the need for constant polling.