- A
Azure Virtual Machines Scale Set with autoscale rules
Why wrong: A Virtual Machine Scale Set requires you to manage virtual machine images, operating system updates, and scaling rules. It incurs cost even when idle because the underlying VMs are running. While it can scale automatically, it is not a serverless or simplest solution for event-driven file processing.
- B
Azure Batch
Why wrong: Azure Batch is designed for large-scale parallel and high-performance computing jobs. It requires you to create and manage a pool of compute nodes. It is overkill for simple event-driven blob processing and introduces management overhead that the team wants to avoid.
- C
Azure Functions with a Blob Storage trigger
Azure Functions is serverless, scales automatically in response to events, and charges only for execution time. Using a Blob Storage trigger, the function runs whenever a new blob is created. This is the simplest solution that meets all requirements: automatic scaling, no cost when idle, and no infrastructure management.
- D
Azure Container Instances
Why wrong: Azure Container Instances allow you to run containers without managing servers. However, they are not inherently event-driven like Azure Functions. To trigger a container instance on a blob upload, you would need additional components such as Azure Logic Apps or an Azure Function, increasing complexity. Also, while you can stop containers to save cost, the default model costs for the container's lifetime.
Quick Answer
The answer is Azure Functions with a Blob Storage trigger because it provides event-driven serverless compute that automatically scales to handle hundreds of simultaneous file uploads while incurring zero cost when idle. This service executes code only when a new blob is created in the container, making it the simplest solution that requires no infrastructure management. On the AZ-900 exam, this scenario tests your understanding of serverless computing versus IaaS or PaaS options—a common trap is choosing Azure Logic Apps (which is also event-driven but designed for workflows, not custom code) or Azure Batch (which requires job scheduling). Remember the key distinction: Azure Functions is the lightweight, code-first serverless compute service, while Blob Storage triggers are its native event source. For the exam, think “Function triggers on blob = serverless auto-scale with zero idle cost.” A helpful memory tip: “Blob drops, Function pops—no cost when it stops.”
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. 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.
A company develops a data processing application that runs only when new files are uploaded to an Azure Blob Storage container. The application must scale automatically to handle hundreds of simultaneous file uploads and must not incur cost when no files are being processed. The development team wants the simplest solution that requires no infrastructure management. Which Azure compute service should they use?
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 Functions with a Blob Storage trigger
Azure Functions with a Blob Storage trigger is the correct choice because it provides an event-driven, serverless compute model that automatically scales to handle hundreds of concurrent file uploads without requiring any infrastructure management. The function executes only when a new blob is created in the container, ensuring zero cost when no files are being processed, and the platform handles scaling out to meet 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.
- ✗
Azure Virtual Machines Scale Set with autoscale rules
Why it's wrong here
A Virtual Machine Scale Set requires you to manage virtual machine images, operating system updates, and scaling rules. It incurs cost even when idle because the underlying VMs are running. While it can scale automatically, it is not a serverless or simplest solution for event-driven file processing.
- ✗
Azure Batch
Why it's wrong here
Azure Batch is designed for large-scale parallel and high-performance computing jobs. It requires you to create and manage a pool of compute nodes. It is overkill for simple event-driven blob processing and introduces management overhead that the team wants to avoid.
- ✓
Azure Functions with a Blob Storage trigger
Why this is correct
Azure Functions is serverless, scales automatically in response to events, and charges only for execution time. Using a Blob Storage trigger, the function runs whenever a new blob is created. This is the simplest solution that meets all requirements: automatic scaling, no cost when idle, and no infrastructure management.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Azure Container Instances
Why it's wrong here
Azure Container Instances allow you to run containers without managing servers. However, they are not inherently event-driven like Azure Functions. To trigger a container instance on a blob upload, you would need additional components such as Azure Logic Apps or an Azure Function, increasing complexity. Also, while you can stop containers to save cost, the default model costs for the container's lifetime.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse Azure Functions with Azure Batch, thinking both are serverless, but Azure Batch requires explicit job and pool management, making it unsuitable for simple event-driven, per-file processing with zero idle cost.
Detailed technical explanation
How to think about this question
Under the hood, Azure Functions uses the Azure WebJobs SDK to bind to Blob Storage triggers, polling the container for new blobs via Azure Storage analytics logs or event grid notifications. The consumption plan scales out to hundreds of instances automatically based on the number of incoming blob events, with a maximum concurrency of 200 instances per function app. In a real-world scenario, this pattern is ideal for processing images or logs as they arrive, where each file triggers a short-lived function execution.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this AZ-900 question test?
Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Functions with a Blob Storage trigger — Azure Functions with a Blob Storage trigger is the correct choice because it provides an event-driven, serverless compute model that automatically scales to handle hundreds of concurrent file uploads without requiring any infrastructure management. The function executes only when a new blob is created in the container, ensuring zero cost when no files are being processed, and the platform handles scaling out to meet demand.
What should I do if I get this AZ-900 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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Last reviewed: Jun 11, 2026
This AZ-900 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-900 exam.
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