The answer is to set the `batchSize` to 1 in the `host.json` file. This configuration forces the Azure Service Bus triggered function to process messages one at a time, ensuring strict message ordering because the trigger’s message pump will not fetch the next message until the current one is fully completed or dead-lettered. On the Microsoft Azure Developer Associate AZ-204 exam, this scenario tests your understanding of how concurrency settings directly impact ordering guarantees in queue-based triggers—a common trap is confusing `maxConcurrentCalls` with `batchSize`, but for Service Bus triggers, `batchSize` controls how many messages are pulled per iteration. Remember the memory tip: “Batch of one, order won’t be undone.”
AZ-204 Develop Azure compute solutions Practice Question
This AZ-204 practice question tests your understanding of develop azure compute solutions. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 an Azure Function that uses a Service Bus queue trigger. You need to ensure that the function processes messages one at a time to guarantee order. Which configuration should you use?
Correct. This ensures one message per function invocation, maintaining order.
B
Set the maxMessages to 1 in the ServiceBusTrigger attribute
Why wrong: The maxMessages attribute is not valid; the correct configuration is the batchSize property in host.json.
C
Set the function to run on a Premium Plan
Why wrong: The Premium Plan does not automatically guarantee single-message processing; it provides more instances and features but not the batching behavior.
D
Set the maxDequeueCount to 1 in host.json
Why wrong: maxDequeueCount controls the number of times a message can be dequeued before moving to poison queue, not the batch size.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the batchSize to 1 in host.json
Option A is correct because setting `batchSize` to 1 in `host.json` forces the Service Bus trigger to process only one message at a time from the queue. This ensures strict message ordering, as the function will not fetch or process the next message until the current one is completed (either successfully or moved to the dead-letter queue). The Service Bus trigger uses a message pump that respects the `batchSize` setting to control concurrency.
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.
✓
Set the batchSize to 1 in host.json
Why this is correct
Correct. This ensures one message per function invocation, maintaining order.
Related concept
Read the scenario before looking for a memorised answer.
✗
Set the maxMessages to 1 in the ServiceBusTrigger attribute
Why it's wrong here
The maxMessages attribute is not valid; the correct configuration is the batchSize property in host.json.
✗
Set the function to run on a Premium Plan
Why it's wrong here
The Premium Plan does not automatically guarantee single-message processing; it provides more instances and features but not the batching behavior.
✗
Set the maxDequeueCount to 1 in host.json
Why it's wrong here
maxDequeueCount controls the number of times a message can be dequeued before moving to poison queue, not the batch size.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse `batchSize` (which controls how many messages are fetched at once) with `maxConcurrentCalls` (which controls how many parallel executions are allowed), and incorrectly assume that setting `maxConcurrentCalls` to 1 in the trigger attribute is the solution, but the attribute does not have a `maxMessages` property.
Detailed technical explanation
How to think about this question
Under the hood, the Service Bus trigger uses a `MessageReceiver` to prefetch messages based on the `PrefetchCount` and the `batchSize` setting. Setting `batchSize` to 1 effectively disables prefetching, so the function processes messages sequentially. In a real-world scenario, if you need to guarantee order for a high-throughput workload, you might also need to use sessions and set `IsSessionsEnabled` to true, but for a simple queue, `batchSize: 1` is the correct approach.
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: Set the batchSize to 1 in host.json — Option A is correct because setting `batchSize` to 1 in `host.json` forces the Service Bus trigger to process only one message at a time from the queue. This ensures strict message ordering, as the function will not fetch or process the next message until the current one is completed (either successfully or moved to the dead-letter queue). The Service Bus trigger uses a message pump that respects the `batchSize` setting to control concurrency.
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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