Question 732 of 997

Develop Azure compute solutions →hardMultiple ChoiceObjective-mapped

Quick Answer

The correct answer is the queue-based load leveling pattern using an Azure Storage Queue. This pattern is essential because when your Azure Function scales out on a Consumption Plan, multiple instances can flood an external API, but the queue decouples the incoming request rate from the processing rate. By buffering all requests in a queue and having the function dequeue messages at a controlled pace—say, 10 per second—you ensure the total throughput never exceeds the API’s limit, even with dozens of instances running. On the AZ-204 exam, this scenario tests your understanding of how to manage external dependencies under dynamic scaling; a common trap is choosing a retry or circuit breaker pattern, which only handles failures after they occur, rather than preventing the rate violation. Remember the key insight: the queue acts as a shock absorber, smoothing spikes into a steady flow. For a memory tip, think “Queue to Curb”—the queue curbs the rate to keep the API happy.

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 runs on a Consumption Plan. The function calls an external API that enforces a rate limit of 10 requests per second. When the function scales out to multiple instances, you must ensure the rate limit is not exceeded. Which pattern should you implement?

Question 1hardmultiple choice

Read the full NAT/PAT explanation →

A
Use a singleton attribute on the function to ensure only one instance runs.
Why wrong: Singleton limits concurrency to one instance but does not control the rate of calls to an external API; the single instance could still exceed the rate limit.
B
Use a static SemaphoreSlim in the function code to limit concurrent calls.
Why wrong: Static variables are not shared across instances in a distributed scale-out environment.
C
Configure the function's host.json to limit concurrency to 1.
Why wrong: This limits concurrent function executions but does not enforce a per-second rate; a single instance can still call the API more than 10 times per second.
D
Use a queue-based load leveling pattern with an Azure Storage Queue.
Messages are queued, and a function processes them at a controlled rate (e.g., using a timer or batching) to respect the API's rate limit, regardless of the number of instances.

Full breakdown with real-world context →

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

✓

Use a queue-based load leveling pattern with an Azure Storage Queue.

Option D is correct because a queue-based load leveling pattern uses an Azure Storage Queue to buffer incoming requests, allowing the function to process them at a controlled rate. This decouples the function's scaling from the external API's rate limit, ensuring that even with multiple function instances, the total request rate does not exceed 10 requests per second. The queue acts as a buffer, and the function can be configured to dequeue and process messages at a fixed rate, effectively smoothing out spikes in demand.

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.

✗
Use a singleton attribute on the function to ensure only one instance runs.
Why it's wrong here
Singleton limits concurrency to one instance but does not control the rate of calls to an external API; the single instance could still exceed the rate limit.
✗
Use a static SemaphoreSlim in the function code to limit concurrent calls.
Why it's wrong here
Static variables are not shared across instances in a distributed scale-out environment.
✗
Configure the function's host.json to limit concurrency to 1.
Why it's wrong here
This limits concurrent function executions but does not enforce a per-second rate; a single instance can still call the API more than 10 times per second.
✓
Use a queue-based load leveling pattern with an Azure Storage Queue.
Why this is correct
Messages are queued, and a function processes them at a controlled rate (e.g., using a timer or batching) to respect the API's rate limit, regardless of the number of instances.
Related concept
Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse concurrency control within a single instance (Options B and C) with global rate limiting across scaled-out instances, leading them to overlook the need for a distributed coordination mechanism like queue-based load leveling.

Detailed technical explanation

How to think about this question

The queue-based load leveling pattern leverages Azure Storage Queues' built-in visibility timeout and message retrieval mechanics to control processing rate. By setting the function's batch size and new batch threshold in host.json (e.g., batchSize: 1, newBatchThreshold: 0), you can ensure that each function instance processes one message at a time, and the total throughput is limited by the number of queue messages dequeued per second. In a real-world scenario, if the external API has a strict rate limit, you might also combine this with a sliding window counter or a distributed rate limiter using Azure Redis Cache for finer control.

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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this AZ-204 question test?

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: Use a queue-based load leveling pattern with an Azure Storage Queue. — Option D is correct because a queue-based load leveling pattern uses an Azure Storage Queue to buffer incoming requests, allowing the function to process them at a controlled rate. This decouples the function's scaling from the external API's rate limit, ensuring that even with multiple function instances, the total request rate does not exceed 10 requests per second. The queue acts as a buffer, and the function can be configured to dequeue and process messages at a fixed rate, effectively smoothing out spikes in demand.

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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