Question 806 of 1,031

Describe Azure architecture and services →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is Azure Functions. This is the correct choice because Azure Functions is a serverless compute service that natively supports an Azure Functions serverless blob trigger event-driven model, meaning it can automatically execute code whenever a new blob is uploaded to Azure Blob Storage. The function runs only during the event, processes the file, and then terminates, ensuring compute resources are consumed only when there is work to do—perfectly matching the requirement for zero idle cost and no server or container management. On the AZ-900 exam, this scenario tests your ability to distinguish between serverless compute (Azure Functions) and container-based or VM-based services; a common trap is choosing Azure Logic Apps, which is for orchestration and workflows, not for running custom code that terminates. Remember the memory tip: “Functions fire on files”—if the task is to run code in response to a blob upload without managing infrastructure, think Azure Functions.

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 is migrating its on-premises batch processing jobs to Azure. The jobs are triggered by file uploads to an on-premises file share. After migration, the files will be uploaded to Azure Blob Storage. The company wants a solution where code runs automatically whenever a new blob is created, with no requirement to manage servers or containers. The code must process the blob and then terminate. Compute resources should be used only when there is a file to process. Which Azure compute service should the company use?

Question 1mediummultiple choice

Read the full NAT/PAT explanation →

A
Azure App Service
Why wrong: Azure App Service is a platform-as-a-service (PaaS) for hosting web apps, REST APIs, and mobile back ends. It runs continuously and is not designed for event-triggered, short-lived executions that automatically start and stop. It also requires an always-on instance, meaning you pay for running the app even when idle.
B
Azure Kubernetes Service (AKS)
Why wrong: AKS is a managed container orchestration service that requires managing a cluster of virtual machines (nodes). While you can run event-driven workloads on AKS using tools like Keda, it involves more operational overhead than a serverless option and does not naturally scale to zero when idle.
C
Azure Functions
Azure Functions is a serverless compute service that runs code in response to events (e.g., blob creation, HTTP requests, queues) and automatically scales. It charges only for execution time, eliminating idle cost. This matches the need for automatic, triggered processing with no infrastructure management.
D
Azure Virtual Machine Scale Sets
Why wrong: Azure Virtual Machine Scale Sets provide a group of load-balanced VMs that can autoscale. However, they require you to manage VMs, install the application code, and handle patching. They incur costs for idle VMs and are not an event-driven serverless compute service.

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

✓

Azure Functions

Azure Functions is the correct choice because it provides a serverless compute service that can be triggered automatically by Azure Blob Storage events (e.g., new blob creation). The code runs only when a blob is uploaded, processes it, and then terminates, ensuring zero compute cost when idle. No servers or containers need to be managed, aligning perfectly with the requirement for event-driven, ephemeral execution.

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 App Service
Why it's wrong here
Azure App Service is a platform-as-a-service (PaaS) for hosting web apps, REST APIs, and mobile back ends. It runs continuously and is not designed for event-triggered, short-lived executions that automatically start and stop. It also requires an always-on instance, meaning you pay for running the app even when idle.
✗
Azure Kubernetes Service (AKS)
Why it's wrong here
AKS is a managed container orchestration service that requires managing a cluster of virtual machines (nodes). While you can run event-driven workloads on AKS using tools like Keda, it involves more operational overhead than a serverless option and does not naturally scale to zero when idle.
✓
Azure Functions
Why this is correct
Azure Functions is a serverless compute service that runs code in response to events (e.g., blob creation, HTTP requests, queues) and automatically scales. It charges only for execution time, eliminating idle cost. This matches the need for automatic, triggered processing with no infrastructure management.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Virtual Machine Scale Sets
Why it's wrong here
Azure Virtual Machine Scale Sets provide a group of load-balanced VMs that can autoscale. However, they require you to manage VMs, install the application code, and handle patching. They incur costs for idle VMs and are not an event-driven serverless compute service.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates may choose Azure App Service (Option A) because they associate it with running code automatically, but fail to recognize that App Service runs continuously and is not designed for event-driven, ephemeral tasks that terminate after processing a single blob.

Detailed technical explanation

How to think about this question

Azure Functions uses a consumption plan where the host is dynamically scaled based on event triggers, and billing is based on per-second resource consumption and number of executions. The Blob Storage trigger leverages Azure Event Grid to detect new blobs and invoke the function, with a default maximum execution timeout of 10 minutes on the consumption plan. In real-world scenarios, this pattern is ideal for ETL pipelines, image resizing, or log processing where each file is processed independently and the function can scale to thousands of concurrent executions.

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.

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-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 — Azure Functions is the correct choice because it provides a serverless compute service that can be triggered automatically by Azure Blob Storage events (e.g., new blob creation). The code runs only when a blob is uploaded, processes it, and then terminates, ensuring zero compute cost when idle. No servers or containers need to be managed, aligning perfectly with the requirement for event-driven, ephemeral execution.

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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