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AZ-204 Exactly-once delivery Practice Question
You are building an API that needs to send notifications to multiple subscribers. Each subscriber has a different callback URL, and you need to ensure each notification is sent exactly once and retried on failure. Which Azure service should you use?
⚠ Common exam trap
Candidates often choose Event Grid for notification routing but overlook the 'exactly once' requirement. Event Grid is at-least-once. Service Bus, with duplicate detection, can achieve exactly-once delivery.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Service Bus.
Azure Service Bus is the correct choice because it supports exactly-once delivery through duplicate detection and can fan out notifications to multiple subscribers using topics and subscriptions. It also provides built-in retry logic on failures. While Event Grid offers at-least-once delivery, only Service Bus can guarantee exactly-once when properly configured.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Azure Event Grid.
Why it's wrong here
Incorrect. Event Grid uses at-least-once delivery, not exactly-once as required. It is suitable for many notification scenarios but does not meet the 'exactly once' requirement.
- ✓
Azure Service Bus.
Why this is correct
Correct. Service Bus topics with duplicate detection provide exactly-once delivery. Subscribers can receive messages and send them to callback URLs via custom handlers, and retries are handled automatically.
- ✗
Azure Notification Hubs.
Why it's wrong here
Incorrect. Notification Hubs are for push notifications to mobile devices, not for sending notifications to arbitrary callback URLs.
- ✗
Azure Queue Storage.
Why it's wrong here
Incorrect. Queue Storage uses at-least-once delivery and is not designed for fan-out to multiple subscribers with different callback URLs.
Go deeper
Related to this question
Learn chapter
Azure Functions Development
Key term
Azure Service Bus
Azure Service Bus is a cloud-based message broker that allows applications, services, and devices to send and receive messages reliably, even when they are not all running at the same time.
Key term
Azure Relay
Azure Relay is a cloud service that securely exposes on-premises web services to the public internet or other cloud applications without opening firewall ports.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-204 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-204 exam.