What is a message broker and why is it needed?

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

Why is a message broker needed:

• Asynchrony: allows applications to exchange data without waiting for a response, increasing performance and resilience.
• Decentralization: system components can operate independently without knowing each other's details.
• Reliability: brokers often ensure guaranteed message delivery and re-sending in case of failures.
• Scalability: simplifies load distribution and integration of new services.

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

Use case example: a microservice sends an event about order creation to the broker, and another microservice subscribed to this event processes it, for example, to update statistics or send notifications.