The answer is to enable sessions on the Service Bus queue and update the function trigger to use sessions. This is correct because sessions create a logical grouping of related messages, locking the entire session for a single consumer, which guarantees both message ordering and exactly-once processing. When a session-enabled trigger processes a message, it holds the session lock until the function completes, preventing any other consumer from receiving duplicate messages from that same session. On the AZ-204 exam, this scenario tests your understanding of how Service Bus sessions solve the dual challenge of ordering and deduplication, often appearing as a trap where candidates mistakenly choose duplicate detection or idempotent functions alone. A common memory tip is to think of sessions as a “conveyor belt” for related items—once a belt is claimed, no one else can grab items from it until the current worker finishes. Remember: for strict ordering and exactly-once, always pair sessions with a session-aware trigger.
AZ-204 Develop Azure compute solutions Practice Question
This AZ-204 practice question tests your understanding of develop azure compute solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are developing a serverless application using Azure Functions that processes order messages from an Azure Service Bus queue. Each order message is approximately 64 KB in size. The function must process messages in order and exactly once. The current implementation uses a Service Bus trigger with batch processing enabled. You notice that occasionally duplicate messages are processed. You need to ensure exactly-once processing while maintaining message ordering. What should you do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable sessions on the Service Bus queue and update the function trigger to use sessions.
Option B is correct because enabling sessions on the Service Bus queue and using a session-enabled trigger guarantees message ordering and exactly-once processing. Sessions group related messages into a logical sequence, and the Service Bus trigger locks the entire session, ensuring that messages within a session are processed in order and that no other consumer can process the same session concurrently. This prevents duplicate processing while maintaining the required ordering.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Disable batch processing in the function trigger and process messages one at a time.
Why it's wrong here
Disabling batching does not prevent duplicate delivery.
✓
Enable sessions on the Service Bus queue and update the function trigger to use sessions.
Why this is correct
Sessions ensure ordered and exactly-once processing within a session.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the lock duration on the Service Bus queue to 5 minutes.
Why it's wrong here
Longer lock duration reduces the chance of duplicate processing but does not guarantee exactly-once.
✗
Set the maxDeliveryCount property on the queue to 1.
Why it's wrong here
This limits retries but duplicates can still occur from other causes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse disabling batch processing or increasing lock duration with solving duplicate processing, but these do not address the root cause of duplicate deliveries; only session-based or duplicate detection mechanisms guarantee exactly-once processing with ordering.
Detailed technical explanation
How to think about this question
Service Bus sessions provide a first-in-first-out (FIFO) guarantee within a session by using a session ID to group messages. When a session-enabled trigger acquires a lock on a session, it holds the lock until the session is complete, preventing other consumers from processing messages in that session. Under the hood, the Service Bus broker uses the session lock to ensure that messages are delivered in order and exactly once, even if the function host restarts or scales out. In real-world scenarios, this is critical for order processing systems where each order must be processed sequentially without duplicates.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-204 question in full detail.
Develop Azure compute solutions — This question tests Develop Azure compute solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable sessions on the Service Bus queue and update the function trigger to use sessions. — Option B is correct because enabling sessions on the Service Bus queue and using a session-enabled trigger guarantees message ordering and exactly-once processing. Sessions group related messages into a logical sequence, and the Service Bus trigger locks the entire session, ensuring that messages within a session are processed in order and that no other consumer can process the same session concurrently. This prevents duplicate processing while maintaining the required ordering.
What should I do if I get this AZ-204 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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