AZ-305 practice question 10 of 35

You have an Azure subscription that contains two applications named App1 and App2. App1 is a sales processing application. When a transaction in App1…

Choose your answer, then check it against the explanation and the full breakdown below.

Domain Design data storage solutions

You have an Azure subscription that contains two applications named App1 and App2. App1 is a sales processing application. When a transaction in App1 requires shipping, a message is added to an Azure Storage account queue, and then App2 listens to the queue for relevant transactions. In the future, additional applications will be added that will process some of the shipping requests based on the specific details of the transactions. You need to recommend a replacement for the storage account queue to ensure that each additional application will be able to read the relevant transactions. What should you recommend?

Answer options

Correct Answer:

Explanation

The requirement is for multiple, distinct applications to process messages based on specific transaction details. An Azure Service Bus topic utilizes a publish/subscribe (pub/sub) pattern, which is ideal for this one-to-many communication scenario. The sales application (App1) can publish all shipping messages to a single topic. Each consuming application, including App2 and any future applications, can create its own subscription to that topic. Crucially, each subscription can have filter rules based on message properties (e.g., shipping destination, item type). This ensures that each application receives only a copy of the messages relevant to its function, fulfilling the core requirement in a scalable and decoupled manner.

Why Incorrect

A. one Azure Service Bus queue: A queue follows a competing consumer pattern where a message is processed by only one receiver, which fails the requirement for multiple applications to process messages.

C. one Azure Data Factory pipeline: Azure Data Factory is a data integration and ETL/ELT orchestration service, not a real-time messaging system designed for application decoupling.

D. multiple storage account queues: This approach would require the producer (App1) to know which queue to send a message to, creating tight coupling and making the system difficult to modify when new applications are added.

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References

1. Microsoft Documentation | Azure Service Bus | Topics and subscriptions: "In contrast to queues

in which each message is processed by a single consumer

topics and subscriptions provide a one-to-many form of communication

in a publish/subscribe pattern. It's useful for scaling to a large number of recipients." This directly supports the need for multiple applications to receive messages.

2. Microsoft Documentation | Azure Service Bus | Subscription filters and actions: "Subscribers can define which messages they want to receive from a topic. These messages are specified in the form of one or more named subscription rules. Each rule consists of a filter condition that selects particular messages...". This directly addresses the requirement for applications to process messages "based on the specific details of the transactions."

3. Microsoft Documentation | Compare Azure messaging services: In the "Service Bus" section

it recommends using "Topics and subscriptions" for a "publish/subscribe" model. It contrasts this with queues

which are for "point-to-point" communication. This comparison clarifies why a topic is superior to a queue for this scenario.

Question 10 of 35

Question breakdown

Tests: Design application architecture: choose a messaging solution
Difficulty: Easy

Key idea: Service Bus topics with filtered subscriptions deliver a copy of each relevant message to many independent consumers (publish/subscribe).

How to reach the answer

Today one consumer reads a storage queue, but more applications will be added later.
Each new application must read the transactions relevant to it, which is a one-to-many requirement.
Queues use competing consumers, so each message is processed only once.
A Service Bus topic lets each application have its own subscription with filter rules on message properties.

Each option

AIncorrect. A queue delivers each message to a single receiver, so multiple applications cannot each get a copy.
BCorrect. A topic with per-application subscriptions and filters gives each consumer its own copy of only the relevant messages.
CIncorrect. Data Factory is a data integration and ETL orchestration service, not an application messaging broker.
DIncorrect. Multiple queues would force App1 to route each message itself, coupling the producer to every new consumer.

Common trap: Choosing a Service Bus queue because it is a richer upgrade from a storage queue, while overlooking that queues are point-to-point.

In practice: Order and shipping systems commonly publish events to a Service Bus topic. Warehouse, billing, and notification services each subscribe with SQL or correlation filters.

Remember: Choose a queue when one consumer should process each message, and a topic when multiple filtered subscribers each need a copy.

Official documentation: Service Bus queues, topics, and subscriptions · Topic filters and actions

Drafted with AI assistance and checked against the answer key.

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