A message broker developer designs, develops, and maintains software systems that facilitate message-based communication between different applications. They ensure seamless data transmission across various platforms using message broker services like RabbitMQ, Apache Kafka, or AWS SQS. They configure and manage message queues, topics, and subscriptions, while considering factors like message persistence, durability, and delivery modes. They also work on fault-tolerance, ensuring messages are not lost during failures. Moreover, they handle message transformation and routing. They may also be involved in troubleshooting and resolving issues related to messaging systems, and often work in tandem with other software developers and IT professionals.