Azure Service Bus Topics and Subscriptions

While queues deliver each message to a single consumer, Service Bus topics enable publish-subscribe patterns where a single message can be delivered to many consumers. Topics are essential for broadcasting events, notifications, and updates across multiple independent services. This lesson covers how topics and subscriptions work, how to use filters to route messages, and practical patterns for real-world systems.

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How Topics and Subscriptions Work

A topic is similar to a queue in that it receives messages from senders. However, instead of delivering messages directly to consumers, the topic distributes copies of each message to one or more subscriptions. Each subscription behaves like a virtual queue that can have its own set of consumers.

                         +---> [ Subscription: billing ] ---> Billing Service
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Producer --> [ Topic ] --+---> [ Subscription: audit ] ---> Audit Service
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                         +---> [ Subscription: email ] ---> Email Service

Key characteristics: