Configure Service Bus Topic Subscriptions with Message Filtering

Azure Service Bus topics implement the publish-subscribe messaging pattern, allowing a single message to be delivered to multiple subscribers simultaneously. Unlike queues, which deliver each message to a single consumer, topics broadcast messages to all matching subscriptions - making them ideal for scenarios like event-driven architectures where different downstream systems need to react to the same event stream. The real power of topics comes from subscription filter rules, which let the broker evaluate message properties and route each message to only the subscriptions whose filters match, eliminating the need for application-level routing logic.

In this lab, you will work with an order processing scenario where different downstream services need different subsets of order messages. You will create topic subscriptions with SQL filter rules to route high-value orders to a fraud check service, international orders to a customs service, and all orders to an analytics service. You will then add a correlation filter for a fourth subscription and send test messages with custom properties to verify that the broker routes each message to the correct subscriptions.

Objectives

Upon completing this Intermediate level lab, you will be able to:

• Create a Service Bus topic and multiple subscriptions using the Azure CLI
• Configure SQL filter rules to route messages based on custom properties such as order value and country
• Implement a catch-all subscription using a default true filter for analytics processing
• Send test messages with application properties and verify correct routing to each subscription
• Add a correlation filter for a fourth subscription and compare behavior with SQL filters
• Test filter priority and observe how messages match multiple subscriptions simultaneously

Who is this lab for?

This lab is designed for:

• Cloud developers preparing for AZ-204 or working with event-driven messaging patterns
• Solution architects designing pub/sub systems with content-based message routing
• Solution Architects architecting event-driven systems using Azure Service Bus topics and subscriptions

Basic familiarity with the Service Bus resource and command-line tools is recommended.