AZ-204 Practice Question: Connect to and consume Azure services and third-party services
A company has an Azure Service Bus namespace with a topic that receives high-throughput messages. They need to ensure that if a subscriber fails, messages are not lost and can be replayed. The subscriber is a client application that uses the PeekLock receive mode. What should they configure?
⚠ Common exam trap
Candidates often think disabling dead-lettering prevents message loss (by keeping messages in the subscription), but in reality, without dead-lettering, messages that cannot be delivered are simply discarded after exceeding the maximum delivery count, leading to permanent loss.
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
✓
Enable dead-lettering on the subscription.
Dead-lettering on a subscription allows messages that cannot be processed by a subscriber to be moved to a dead-letter queue (DLQ) instead of being lost. When a subscriber using PeekLock mode fails to process a message (e.g., exceeds MaxDeliveryCount or the lock expires), the message is automatically transferred to the DLQ. This ensures messages are preserved and can be replayed later by reprocessing the DLQ, meeting the requirement for no message loss and replay capability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable auto-forwarding on the subscription.
Why it's wrong here
Enabling auto-forwarding on a subscription automatically moves messages from the current subscription to another specified queue or topic after they are successfully received. This feature is primarily used for chaining messaging entities or simplifying client code by abstracting the final destination, rather than providing a mechanism for handling messages that fail processing within the current subscription. It does not offer fault tolerance for messages that encounter errors during consumption.
- ✗
Set a SQL filter on the subscription.
Why it's wrong here
Setting a SQL filter on a subscription allows messages to be selectively delivered from a topic based on specific criteria defined in a SQL-like expression, such as message properties or custom user properties. While essential for message routing and ensuring only relevant messages reach a subscriber, this filtering occurs *before* message delivery attempts. It provides no mechanism for fault tolerance or recovery for messages that fail to be processed *after* they have been successfully received by the subscription.
- ✗
Disable dead-lettering on the subscription.
Why it's wrong here
Disabling dead-lettering on a subscription means that messages which fail to be processed successfully after exceeding the configured MaxDeliveryCount, or those that expire due to their TimeToLive, will be permanently lost. Without a Dead-Letter Queue (DLQ), there is no facility to inspect these problematic messages, diagnose the root cause of processing failures, or manually re-submit them for another attempt. This approach actively prevents fault tolerance and message recovery, making it unsuitable for robust, mission-critical systems.
- ✓
Enable dead-lettering on the subscription.
Why this is correct
Enabling dead-lettering on a subscription automatically moves messages that cannot be delivered or processed successfully into a special sub-queue called the Dead-Letter Queue (DLQ). Messages are typically dead-lettered if they exceed the MaxDeliveryCount, expire, or if there are issues with subscription filters. This provides a crucial fault-tolerance mechanism, allowing operators to inspect failed messages, diagnose the root cause of processing errors, and potentially re-submit them for processing after corrective action, preventing data loss and enabling message recovery.
Go deeper
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Key term
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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.
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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.