Azure Service Bus: Messaging Patterns

Service Bus is Azure’s fully managed enterprise message broker. It supports Queues (point-to-point) and Topics/Subscriptions (pub/sub). Choosing the right pattern prevents architectural headaches.

Queues vs Topics

graph LR
    subgraph Queue
        Sender1[Sender] --> Q[Queue]
        Q --> Receiver1[Receiver]
    end
    
    subgraph TopicSub ["Topic & Subscriptions"]
        Publisher[Publisher] --> Topic[Topic]
        Topic --> SubA[Subscription A]
        Topic --> SubB[Subscription B]
    end
    
    style Topic fill:#E1F5FE

Dead-Letter Queue

Messages that fail processing N times go to a special DLQ for inspection and replay.

Key Takeaways

• Use **Sessions** for ordered processing (FIFO for a specific session ID).
• Use **Duplicate Detection** if your senders might retry.