What message brokers have you worked with?

In frontend development, message brokers are most commonly used, integrated via WebSocket or specialized real-time services. For example, I have worked with brokers such as:

• Socket.IO — for bidirectional communication between client and server.
• Firebase Realtime Database and Firestore — for real-time data synchronization.
• MQTT — in IoT projects, where the frontend subscribes to messages via WebSocket.

For more complex systems with backend microservices, RabbitMQ or Kafka are often used, but on the frontend, interaction occurs through APIs or WebSocket protocols.