AZ-305 - Design Infrastructure Solutions (38% of the exam) - Section 4.2

Design application architecture solutions including microservices, messaging, and API management.

Design microservices architectures that use Azure Service Bus for reliable messaging, Azure Event Grid for event-driven integration, and Azure API Management to expose and govern APIs. Recognise when Azure Logic Apps is the appropriate orchestration choice and apply microservices patterns to decouple services and handle failure gracefully.

Azure Service BusAzure Event GridAzure API ManagementAzure Logic Appsmicroservices patterns

Practice question for this objective

Free sampleDesign Infrastructure Solutionsmedium

An order-processing platform issues 'PlaceOrder' instructions that must be processed exactly once, can never be duplicated, and require dead-letter handling for any message the worker cannot process. Which Azure messaging service fits these command-style requirements?

AUse Azure Event Grid topics with CloudEvents schema and webhook handlers.
BUse Azure Service Bus queues for the PlaceOrder workflow with peek-lock receivers. Correct
CUse Azure Event Hubs with multiple partitions and consumer groups.
DUse Azure Storage Queues with 7-day retention and visibility timeout.

Commands belong on Service Bus; Event Grid and Event Hubs handle events and streams, not transactional instructions. The architecture guide defines commands as high-value messages that must be delivered at least once and processed at most once, with dead-letter handling for poison messages. Service Bus is the only Azure service that supplies peek-lock receive, duplicate detection, transactions, sessions, and a built-in dead-letter queue together.

Why A is wrong: Event Grid is optimised for discrete events with at-least-once push semantics and explicitly does not provide duplicate detection or transactional guarantees that PlaceOrder commands require.

Why B is correct: Correct. The architecture guide defines commands as high-value messages that must be delivered at least once and processed at most once, with dead-letter handling for poison messages.

Why C is wrong: Event Hubs is a log-based streaming service tuned for high-volume telemetry and has no dead-letter queue or duplicate-detection facility for individual command processing.

Why D is wrong: Storage Queues lack dead-letter queues, duplicate detection, and transactions, so they cannot satisfy the strict command-processing requirements stated.

See more AZ-305 practice questions, answers explained.

Exam traps in Design Infrastructure Solutions

Answers that look right on this material and are not. Each one is a distractor from a different question in the AZ-305 bank for this domain.

Strictly ordered processing with sessions and transactions belongs on Event Grid.
Why it is wrong: Event Grid does not provide sessions, transactions, or guaranteed ordering, and the docs explicitly redirect those workloads to Service Bus.
Azure SQL Database tables via direct row inserts.
Why it is wrong: Azure SQL Database is not a documented Event Grid push handler; integration with SQL goes through a compute layer such as Functions or Logic Apps.
REST access through standard storage account credentials.
Why it is wrong: REST access through storage credentials describes Storage Queues, not a Service-Bus-exclusive capability.

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