- A
In all three models, Microsoft is responsible for securing the physical datacenter and network infrastructure. For IaaS, the customer is responsible for the guest OS and applications; for PaaS, the customer is responsible for the application code and data; for SaaS, the customer is responsible for data and user accounts.
This option correctly describes the shared responsibility divisions: physical security is always Microsoft's responsibility; under IaaS the customer manages OS/apps; under PaaS the customer manages code/data; under SaaS the customer manages data and accounts.
- B
In IaaS, Microsoft is responsible for the guest OS; in PaaS, Microsoft is responsible for the application code; in SaaS, the customer is responsible only for data.
Why wrong: This is incorrect because in IaaS the customer is responsible for the guest OS, not Microsoft. In PaaS, the customer is responsible for the application code. In SaaS, the customer is responsible for data and user access, not just data.
- C
In IaaS, the customer is responsible for everything from the physical infrastructure up; in PaaS, Microsoft is responsible for the application runtime and the customer is responsible only for data; in SaaS, Microsoft is responsible for everything.
Why wrong: This is incorrect because in IaaS, Microsoft is responsible for the physical infrastructure (datacenter, networking, servers). In PaaS, the customer is also responsible for application code and data, not just data. In SaaS, the customer is responsible for data and user access, not nothing.
- D
In all three models, the customer is responsible for securing all application code and data, while Microsoft secures the underlying hardware and operating system.
Why wrong: This is incorrect because the division of responsibility varies by model. For IaaS, the customer secures the OS; for SaaS, Microsoft secures the underlying OS and application; the customer does not have full responsibility for application code in all models.
Quick Answer
The correct answer is Option A because it precisely maps the division of security responsibilities across IaaS, PaaS, and SaaS under the Microsoft shared responsibility model. The core principle is that Microsoft always secures the physical datacenter and network infrastructure, while the customer’s duties shift depending on the service model: with IaaS like Azure VMs, you manage the guest OS and applications; with PaaS like Azure App Service, you handle the application code and data; and with SaaS like Dynamics 365, you are responsible only for your data and user accounts. On the AZ-900 exam, this concept tests your understanding of how responsibility boundaries change as you move up the cloud stack—a common trap is assuming Microsoft handles everything in PaaS or that the customer controls the physical hardware in IaaS. A reliable memory tip is to think of the “layers of the stack”: as you go from IaaS to PaaS to SaaS, Microsoft takes over more layers, leaving you with less to manage, but you always own your data and identities.
AZ-900 Describe cloud concepts Practice Question
This AZ-900 practice question tests your understanding of describe cloud concepts. 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 planning to migrate its customer relationship management (CRM) system to the cloud. The company is evaluating three service models: deploying the CRM on Azure Virtual Machines (IaaS), using Azure App Service to host a custom CRM web application (PaaS), and subscribing to a cloud-based CRM software like Dynamics 365 (SaaS). According to the Microsoft shared responsibility model, which of the following statements accurately describes the division of security responsibilities across these three options?
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
In all three models, Microsoft is responsible for securing the physical datacenter and network infrastructure. For IaaS, the customer is responsible for the guest OS and applications; for PaaS, the customer is responsible for the application code and data; for SaaS, the customer is responsible for data and user accounts.
Option A is correct because it accurately reflects the Microsoft shared responsibility model across IaaS, PaaS, and SaaS. In all three models, Microsoft is responsible for the physical datacenter and network infrastructure. For IaaS (Azure VMs), the customer manages the guest OS and applications; for PaaS (Azure App Service), the customer manages the application code and data; for SaaS (Dynamics 365), the customer manages data and user accounts. This division aligns with the principle that responsibility shifts from the customer to Microsoft as the service model moves from IaaS to SaaS.
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.
- ✓
In all three models, Microsoft is responsible for securing the physical datacenter and network infrastructure. For IaaS, the customer is responsible for the guest OS and applications; for PaaS, the customer is responsible for the application code and data; for SaaS, the customer is responsible for data and user accounts.
Why this is correct
This option correctly describes the shared responsibility divisions: physical security is always Microsoft's responsibility; under IaaS the customer manages OS/apps; under PaaS the customer manages code/data; under SaaS the customer manages data and accounts.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
In IaaS, Microsoft is responsible for the guest OS; in PaaS, Microsoft is responsible for the application code; in SaaS, the customer is responsible only for data.
- ✗
In IaaS, the customer is responsible for everything from the physical infrastructure up; in PaaS, Microsoft is responsible for the application runtime and the customer is responsible only for data; in SaaS, Microsoft is responsible for everything.
Why it's wrong here
This is incorrect because in IaaS, Microsoft is responsible for the physical infrastructure (datacenter, networking, servers). In PaaS, the customer is also responsible for application code and data, not just data. In SaaS, the customer is responsible for data and user access, not nothing.
- ✗
In all three models, the customer is responsible for securing all application code and data, while Microsoft secures the underlying hardware and operating system.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume Microsoft is responsible for the guest OS in IaaS or that the customer is responsible for everything in IaaS, confusing the layered responsibility boundaries across the three service models.
Detailed technical explanation
How to think about this question
The shared responsibility model is defined by the abstraction level of the service: in IaaS, the customer controls the guest OS, middleware, and applications; in PaaS, the customer controls only the application and data, while Microsoft manages the runtime, OS, and infrastructure; in SaaS, the customer controls data and identity, while Microsoft manages everything else. This model is codified in Microsoft's documentation and is critical for compliance frameworks like SOC 2 and ISO 27001, where responsibility boundaries must be clearly defined. A real-world scenario: if a customer deploys a custom CRM on Azure App Service (PaaS) and fails to secure the application code, they are liable for a data breach, even though Microsoft secures the underlying platform.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
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FAQ
Questions learners often ask
What does this AZ-900 question test?
Describe cloud concepts — This question tests Describe cloud concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: In all three models, Microsoft is responsible for securing the physical datacenter and network infrastructure. For IaaS, the customer is responsible for the guest OS and applications; for PaaS, the customer is responsible for the application code and data; for SaaS, the customer is responsible for data and user accounts. — Option A is correct because it accurately reflects the Microsoft shared responsibility model across IaaS, PaaS, and SaaS. In all three models, Microsoft is responsible for the physical datacenter and network infrastructure. For IaaS (Azure VMs), the customer manages the guest OS and applications; for PaaS (Azure App Service), the customer manages the application code and data; for SaaS (Dynamics 365), the customer manages data and user accounts. This division aligns with the principle that responsibility shifts from the customer to Microsoft as the service model moves from IaaS to SaaS.
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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