What is a message broker?

A message broker is a software component that facilitates the transfer of messages between different applications or services in a distributed system. It acts as an intermediary, receiving messages from senders and delivering them to recipients, ensuring asynchronous and reliable communication.

Main functions of a message broker:

• Buffering messages so that the sender and receiver are not dependent on simultaneous operation.
• Routing messages through the appropriate channels or queues.
• Delivery guarantees (e.g., "delivered at least once" or "exactly once").
• Support for various protocols and message formats.

Examples of popular message brokers: RabbitMQ, Apache Kafka, ActiveMQ.

Example of usage: a microservice sends an event about order creation to a queue, the broker delivers this message to the payment processing service, which can process it at a convenient time.