AZ-900 · Domain 1 of 3

AZ-900 Domain 1: Describe cloud concepts

This domain establishes the cloud vocabulary the rest of AZ-900 assumes. It covers what cloud computing is, the shared responsibility model, the public, private and hybrid cloud models, the economics of consumption-based pricing, and the IaaS, PaaS and SaaS service types.

Exam format
25–30%
Official functional groups
3
Assessment estimate
11–16
Suggested study time estimate
5–10 hrs

About 10 min read Reviewed October 2026

Overview

Describe cloud concepts is the foundation of the Azure Fundamentals exam. It has three objective groups. Describing cloud computing covers defining the cloud, the shared responsibility model, the public, private and hybrid cloud models and their use cases, the consumption-based model, cloud pricing models and serverless. Describing the benefits covers high availability, scalability, elasticity, reliability, predictability, security, governance and manageability. Describing cloud service types covers infrastructure as a service, platform as a service and software as a service, and the use cases for each.

At 25–30%, this is a core conceptual group. It is not about Azure services specifically but about understanding why the cloud is used and how responsibility and cost models work. These ideas recur throughout the exam, since the architecture and management groups build on the shared responsibility model, the service types and the economic concepts introduced here.

How it's tested

AZ-900 questions are recognition-level, asking which concept, model or benefit fits a described situation. In this domain they describe a business goal or responsibility and ask which cloud model, service type or economic concept applies, favoring clear definitions over configuration. Read the scenario for which concept it illustrates.

  • Cloud model or service type

    A deployment or responsibility situation is described, and you choose the cloud model or the IaaS, PaaS or SaaS type.

  • Name the benefit

    A business goal is described, and you choose the cloud benefit it illustrates, such as elasticity or high availability.

  • Economic concept

    A cost or responsibility situation is described, and you choose CapEx, OpEx, the consumption model or the shared responsibility split.

Reasoning it through

A company wants to run a web application without managing the operating system or servers, writing only its code. Infrastructure as a service still requires managing the OS, and software as a service is a finished application. Platform as a service provides a managed platform where the provider handles the OS and runtime and the customer deploys code, which matches the requirement, so PaaS is the service type.

Functional groups 3

Official functional groups from the Microsoft outline, in outline order.

1.1 Describe cloud computingCloud definition, shared responsibility, cloud models, consumption pricing and serverless.
What it means
This covers defining cloud computing, the shared responsibility model between provider and customer, the public, private and hybrid cloud models and their use cases, the consumption-based model, cloud pricing models and serverless computing.
What to understand
Cloud computing delivers computing over the internet on demand. The shared responsibility model divides security and management between the provider and the customer, shifting with the service type. Public cloud is shared and provider-owned, private cloud is dedicated, and hybrid combines both. Consumption-based pricing charges only for what is used.
How it shows up
A deployment or responsibility situation is described, and you must choose the cloud model or identify the shared responsibility split.
Common confusion
Confusing the cloud models (public, private, hybrid) with the service types (IaaS, PaaS, SaaS); the models describe where the cloud runs, while the types describe what is managed.
1.2 Describe the benefits of using cloud servicesHigh availability, scalability, elasticity, reliability, security and manageability.
What it means
This covers the benefits of the cloud: high availability and scalability, reliability and predictability, security and governance, and manageability. Each is a reason organizations adopt the cloud.
What to understand
High availability keeps services running despite failures. Scalability is the ability to grow, while elasticity automatically matches capacity to demand. Reliability and predictability come from redundant, well-architected infrastructure. Security and governance are built in, and manageability comes from automation and managed services.
How it shows up
A business goal is described, and you must name the cloud benefit it illustrates, such as elasticity or high availability.
Common confusion
Confusing scalability with elasticity; scalability is the ability to grow, while elasticity automatically scales up and down with demand.
1.3 Describe cloud service typesIaaS, PaaS and SaaS and their use cases.
What it means
This covers the three cloud service types: infrastructure as a service, platform as a service and software as a service, and the appropriate use cases for each, framed by how much the provider manages versus the customer.
What to understand
IaaS provides virtualized infrastructure where the customer manages the operating system and up. PaaS provides a managed platform where the customer deploys code and the provider manages the OS and runtime. SaaS is a finished application the customer simply uses. More provider management means less customer control and effort.
How it shows up
A management or responsibility need is described, and you must choose IaaS, PaaS or SaaS.
Common confusion
Confusing PaaS with IaaS; in IaaS the customer manages the operating system, while in PaaS the provider does.

High-yield concepts

The terms, rules and formulas this domain turns into questions most often.

  • Shared responsibility model

    Security and management split between provider and customer.

    Remember
    The split shifts with the service type.
    Tested as
    Foundational responsibility questions.
    Trap
    Applying one split to every service type.

  • Public vs. private vs. hybrid cloud

    Shared provider cloud, dedicated cloud, and a combination.

    Remember
    They describe where the cloud runs.
    Tested as
    Cloud model questions.
    Trap
    Confusing models with service types.

  • IaaS vs. PaaS vs. SaaS

    Infrastructure, managed platform, and finished application.

    Remember
    More provider management means less customer control.
    Tested as
    Service type questions.
    Trap
    Confusing PaaS with IaaS over who manages the OS.

  • Scalability vs. elasticity

    The ability to grow versus automatic matching of capacity to demand.

    Remember
    Elasticity is automatic and bidirectional.
    Tested as
    Benefit questions.
    Trap
    Using the terms interchangeably.

  • High availability

    Keeping services running despite failures.

    Remember
    It minimizes downtime through redundancy.
    Tested as
    Benefit questions.
    Trap
    Confusing it with scalability.

  • CapEx vs. OpEx

    Upfront capital expense versus ongoing operating expense.

    Remember
    The cloud shifts spending to OpEx.
    Tested as
    Economics questions.
    Trap
    Confusing the two expense models.

  • Consumption-based model

    Paying only for the resources used.

    Remember
    No upfront hardware purchase.
    Tested as
    Economics questions.
    Trap
    Confusing it with fixed pricing.

  • Serverless

    Running code without managing servers, billed per use.

    Remember
    The provider handles all infrastructure.
    Tested as
    Concept questions.
    Trap
    Thinking there are no servers at all.

  • Reliability and predictability

    Consistent, dependable performance from well-architected infrastructure.

    Remember
    Redundancy underpins reliability.
    Tested as
    Benefit questions.
    Trap
    Confusing reliability with security.

  • Manageability

    Easier management through automation and managed services.

    Remember
    It reduces operational effort.
    Tested as
    Benefit questions.
    Trap
    Overlooking it as a cloud benefit.

Side by side

Concepts candidates mix up, compared on the point that decides the answer.

Public vs. private vs. hybrid cloud

ConceptMeaningKey differenceCommon trap
Public cloud Shared, provider-owned infrastructure Lowest management, shared Confusing it with a service type
Private cloud Dedicated infrastructure for one organization More control, more cost Assuming it must be on-premises
Hybrid cloud A combination of public and private Flexibility across both Confusing it with multi-cloud

IaaS vs. PaaS vs. SaaS

ConceptMeaningKey differenceCommon trap
IaaS Virtualized infrastructure Customer manages the OS and up Expecting the provider to manage the OS
PaaS Managed platform for code Provider manages the OS and runtime Confusing it with IaaS
SaaS Finished application Customer just uses it Expecting to manage infrastructure

Scalability vs. elasticity vs. high availability

ConceptMeaningKey differenceCommon trap
Scalability The ability to grow capacity Growth, not automatic Treating it as automatic
Elasticity Automatic matching of capacity to demand Automatic and bidirectional Confusing it with scalability
High availability Staying up despite failures Minimizes downtime Confusing it with scalability

Exam traps

Each trap is an answer that looks right. Learn the clue that should change your mind.

  1. Model is a service type

    What candidates pick
    Answer a hybrid-versus-public question with IaaS or SaaS.
    Why it looks right
    All are cloud terms.
    Why it's wrong
    Cloud models describe where the cloud runs; service types describe what is managed. The question asks for one or the other.

    Clue to watch for The scenario is about deployment location versus management responsibility.

  2. PaaS manages nothing

    What candidates pick
    Treat PaaS as requiring the customer to manage the operating system.
    Why it looks right
    IaaS does require that.
    Why it's wrong
    In PaaS the provider manages the OS and runtime; the customer deploys code.

    Clue to watch for The customer wants to deploy code without managing servers or the OS.

  3. Scalability is elasticity

    What candidates pick
    Call automatic capacity matching scalability.
    Why it looks right
    Both involve capacity.
    Why it's wrong
    Elasticity automatically matches capacity to demand; scalability is the ability to grow.

    Clue to watch for The scenario describes capacity automatically rising and falling.

  4. Capex still applies

    What candidates pick
    Describe cloud spending as upfront capital purchase.
    Why it looks right
    Hardware was bought upfront traditionally.
    Why it's wrong
    The cloud shifts spending to operating expense, paying for usage without buying hardware.

    Clue to watch for The benefit is avoiding upfront hardware purchases.

  5. Serverless has no servers

    What candidates pick
    Assume serverless means literally no servers exist.
    Why it looks right
    The name suggests it.
    Why it's wrong
    Servers exist but the provider manages them entirely, and the customer never sees or configures them.

    Clue to watch for The scenario is about not managing infrastructure, not the absence of servers.

  6. One responsibility split

    What candidates pick
    Apply the same shared responsibility split to IaaS and SaaS.
    Why it looks right
    It is one model.
    Why it's wrong
    The split shifts with the service type; the customer manages more in IaaS than in SaaS.

    Clue to watch for The service type changes who is responsible.

Answer framework

For any Domain 1 concept scenario, use these steps to find the answer AZ-900 expects.

  1. Decide whether the question is about a cloud model, a service type, a benefit or an economic concept, since each has its own vocabulary.
  2. For deployment location, choose the cloud model: public for shared, private for dedicated, hybrid for a combination.
  3. For responsibility, choose the service type by who manages the OS: IaaS (customer), PaaS (provider manages OS, customer deploys code) or SaaS (finished application).
  4. For benefits, match the goal to the precise term, distinguishing scalability, elasticity and high availability.
  5. For economics, identify the concept, such as CapEx versus OpEx or the consumption-based model, and apply the shared responsibility split for the service type.

Practice question

A development team wants to deploy a web application and have the cloud provider manage the operating system, runtime and underlying servers, while the team provides only the application code. Which cloud service type BEST fits this requirement?

Want more like this? The AZ-900 practice test has questions for every domain.

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Study strategy

Treat this domain as learning the language of the cloud, since every other part of AZ-900 uses it. Start with the two sets of terms candidates most confuse: the cloud models (public, private, hybrid), which describe where the cloud runs, and the service types (IaaS, PaaS, SaaS), which describe what is managed. Drill the IaaS-versus-PaaS distinction over who manages the operating system.

Next, learn the shared responsibility model and how it shifts with the service type, and the benefits, nailing the scalability-versus-elasticity difference. Then cover the economics: CapEx versus OpEx, the consumption model and serverless.

Because AZ-900 is a recognition exam, clear definitions and short practice questions are more valuable than hands-on labs here. The free Microsoft Learn Azure Fundamentals path maps directly to these objectives. Afterwards, move to Domain 2, Azure architecture and services, the largest group. Because AZ-900 is a recognition exam, flashcards and timed practice questions are more valuable than hands-on labs, and reviewing missed questions by group shows where to focus.

FAQ

How much of AZ-900 is Domain 1?

Describe cloud concepts is 25–30% of the exam, a core conceptual group whose ideas recur across the exam.

What is the difference between a cloud model and a service type?

A cloud model (public, private, hybrid) describes where the cloud runs. A service type (IaaS, PaaS, SaaS) describes how much the provider manages versus the customer.

What is the difference between IaaS and PaaS?

In IaaS the customer manages the operating system and everything above it. In PaaS the provider manages the OS and runtime, and the customer deploys only application code.

What is the shared responsibility model?

A division of security and management duties between the provider and the customer. The split shifts with the service type, with the customer responsible for more in IaaS than in SaaS.

What is the difference between scalability and elasticity?

Scalability is the ability to grow capacity. Elasticity automatically matches capacity to demand, scaling up and down as needed.

What is CapEx versus OpEx?

Capital expenditure is upfront spending on assets such as hardware. Operating expenditure is ongoing spending on usage. The cloud shifts spending from CapEx to OpEx.

How does Domain 1 connect to the rest of the exam?

It establishes the cloud value, responsibility model and service types that the architecture and management groups build on.

Other Cloud Computing certifications

Where the same subject shows up in other exams. Cards marked "Same subject" open the matching domain.

Test your Domain 1 knowledge

You have covered cloud computing, the shared responsibility model, cloud models, economics and service types. Test whether you can name the right concept for a scenario under exam conditions.

Take the AZ-900 practice test Check your AZ-900 readiness

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