1.1 What Is Cloud Computing?

Microsoft Azure Fundamentals AZ-900

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1 Introduction

About the Microsoft Azure Fundamentals (AZ-900) Exam Study Strategies and Exam Tips

2 Domain 1: Cloud Concepts (25-30%)

1.1 What Is Cloud Computing? 1.2 Cloud Service Models (IaaS, PaaS, SaaS) 1.3 Cloud Deployment Models (Public, Private, Hybrid) 1.4 The Consumption-Based Model

3 Domain 2A: Azure Architecture Components

2.1 Azure Regions and Availability Zones 2.2 Azure Resource Hierarchy (Management Groups, Subscriptions, Resource Groups) 2.3 Azure Resource Manager (ARM) Overview

4 Domain 2B: Azure Compute Services

2.3 Azure Virtual Machines 2.4 Azure App Service, Containers, and Serverless 2.5 Azure Virtual Desktop

5 Domain 2C: Azure Networking Services

2.6 Azure Virtual Networks (VNet) 2.7 Azure VPN Gateway and ExpressRoute 2.8 Azure Load Balancing and Content Delivery

6 Domain 2D: Azure Storage Services

2.9 Azure Storage Accounts and Services 2.10 Azure Database Services 2.11 Azure Data Services and Analytics

7 Domain 2E: Azure Identity, Access, and Security

2.11 Microsoft Entra ID (Azure Active Directory) 2.12 Azure RBAC, Zero Trust, and Defense in Depth 2.13 Azure Security Services

8 Domain 3A: Azure Cost Management

3.1 Factors That Affect Azure Costs 3.2 Azure Pricing Calculator and Cost Management 3.3 Using Tags for Cost Management and Organization

9 Domain 3B: Azure Governance and Compliance

3.3 Azure Policy 3.4 Resource Locks and Tags 3.5 Azure Blueprints, ARM Templates, and Bicep 3.6 Azure Governance Features: Putting It All Together

10 Domain 3C: Azure Monitoring and Management Tools

3.6 Azure Monitor and Service Health 3.7 Azure Compliance, Privacy, and Trust 3.8 Azure Activity Log, Diagnostics, and Resource Health

11 Additional Azure Services and Exam Review

Azure AI and Machine Learning Services Azure IoT and DevOps Services AZ-900 Exam Review: Key Concepts Summary Common AZ-900 Exam Scenarios and Practice

12 Advanced Azure Topics and Service Deep Dives

Azure Migration Services and Tools High Availability and Disaster Recovery in Azure Azure Networking: Private Link, Service Endpoints, and Bastion Azure Management Tools: Portal, CLI, PowerShell, and Cloud Shell Azure SLAs, Service Lifecycle, and Support Plans

1.1 What Is Cloud Computing?

Key Takeaways Explain This Topic AI

Cloud computing is the on-demand delivery of computing services (compute, storage, databases, networking, software, analytics, AI) over the internet, billed by consumption.

The core financial shift is from Capital Expenditure (CapEx) for owned hardware to Operating Expenditure (OpEx) for rented, variable-cost services.

NIST defines cloud computing through five essential characteristics: on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service.

Cloud benefit terms to know for AZ-900: high availability, scalability, elasticity, agility, reliability, predictability, security, governance, and manageability.

Scalability is the ability to add or remove resources (manual or automatic); elasticity is the AUTOMATIC, demand-driven version of scaling.

Last updated: October 2026

Quick Answer: Cloud computing is the delivery of computing services — servers, storage, databases, networking, software, analytics, and intelligence — over the internet ("the cloud"). You rent capacity on demand and pay only for what you consume, trading large upfront hardware purchases (CapEx) for variable operating costs (OpEx).

Exam Context

Microsoft doesn't publish the AZ-900 question count (most Microsoft exams have 40-60 questions ). The AZ-900: Microsoft Azure Fundamentals exam gives you 45 minutes of answering time (about 65 minutes of total seat time), and requires a scaled score of 700 out of 1000 to pass. The fee is USD $99 (regional pricing varies). Domain 1, Describe cloud concepts , is worth 25-30% of the exam. These are vocabulary and scenario questions, not calculations. Memorize the precise meaning of each benefit term, because Microsoft writes distractors using adjacent words (scalability vs elasticity, availability vs reliability).

The NIST Definition

The National Institute of Standards and Technology (NIST) provides the widely accepted definition of cloud computing through five essential characteristics:

Characteristic Meaning Azure Example

On-demand self-service Provision resources yourself, anytime, without contacting the provider Spin up a VM from the Azure portal, CLI, or ARM template in minutes

Broad network access Reach services over standard networks from any device Access Azure from a laptop, phone, or REST API over HTTPS

Resource pooling The provider's hardware is multi-tenant and shared among many customers Many tenants run isolated VMs on the same physical host

Rapid elasticity Capacity expands and contracts quickly, often automatically VM Scale Sets add instances when CPU rises, remove them when it falls

Measured service Usage is metered, controlled, and billed transparently Azure Cost Management reports compute usage and per-GB storage

• Traditional IT vs Cloud Computing
• Traditional (on-premises)

Buy hardware upfront — servers, SAN storage, switches, firewalls.

Build and staff data centers — power, cooling, physical security, fire suppression.

Guess capacity months ahead: over-provision (wasted money) or under-provision (outages).

Own all maintenance — patching, firmware, hardware replacement, refresh cycles.

Capital expenditure (CapEx): large up-front spend, depreciated over years.

Slow provisioning: weeks to months to procure and rack new gear.

Cloud (Azure)

Rent on demand — no hardware purchases.

Microsoft runs the data centers , hardware, cooling, power, and physical security.

Scale dynamically in minutes to match real demand.

Pay only for what you use with per-second or per-minute granularity.

Operating expenditure (OpEx): variable, consumption-based, deductible in-year.

Fast provisioning: seconds to minutes.

The Benefits Vocabulary

Microsoft groups cloud benefits into a specific set of terms. Map each scenario word to the right term:

High availability — the service stays reachable. Azure publishes uptime in Service Level Agreements (SLAs) such as 99.9% or 99.99%.

Reliability — the system recovers from failures and keeps working (resilience). Closely paired with disaster recovery and the design of resources across regions and availability zones.

Scalability — add/remove capacity to meet demand. Vertical = scale up/down (a bigger VM, e.g., 4 vCPU to 8 vCPU). Horizontal = scale out/in (more instances, e.g., 2 VMs to 10).

Elasticity — scaling that happens automatically in response to live metrics (CPU, memory, queue length).

Agility — deploy and reconfigure in minutes instead of weeks, so teams experiment faster.

Predictability — both cost predictability (Pricing Calculator, Cost Management) and performance predictability (autoscale, load balancing).

Security — defense-in-depth, encryption, and tools like Microsoft Defender for Cloud.

Governance — enforce standards with Azure Policy, resource locks, and tags.

Manageability — manage of the cloud (autoscale, alerts) and in the cloud (portal, CLI, templates).

CapEx vs OpEx

• Aspect CapEx (Capital Expenditure) OpEx (Operating Expenditure)
• Definition Up-front spend on physical assets Pay for products/services as consumed
• Payment Large one-time purchase Pay-as-you-go, monthly invoice
• Accounting Depreciated over useful life Deducted in the same year
• Example $100,000 for servers $5,000/month for Azure VMs
• Flexibility Low — locked to purchased gear High — scale up or down freely
• Risk Over-provisioning, obsolescence Pay only for what you use

Common Trap: A scenario that says "automatically add servers during a Black Friday spike" is elasticity , not plain scalability. A scenario that says "the website kept serving users even when one data center failed" is reliability/high availability , not scalability.

Worked Scenario: Reading the Vocabulary

Consider a startup that today owns ten servers in a leased rack. Three problems recur. First, every December its traffic triples and the servers cannot keep up, so checkout fails — this is a scalability and elasticity gap, because the company cannot add capacity fast enough, let alone automatically. Second, when one server's power supply dies, an entire service goes offline for hours — a reliability and high availability gap, because there is no redundancy or fast failover. Third, the finance team cannot predict next quarter's hardware bill — a cost predictability gap.

Moving to Azure addresses each one with a distinct benefit term, and AZ-900 expects you to map the symptom to the term:

December spikes are absorbed by VM Scale Sets that autoscale (elasticity) and can scale out across more instances (horizontal scalability).

A failed component no longer causes downtime because resources are spread across availability zones and backed by an SLA (high availability and reliability).

The finance team uses the Azure Pricing Calculator and Cost Management to forecast and track spend (cost predictability and manageability).

Distinguishing the Easily-Confused Pairs

Confused Pair Key Difference

Scalability vs Elasticity Scalability is the ability to add/remove capacity; elasticity is doing it automatically in response to demand

Availability vs Reliability Availability = is it reachable now (uptime %); reliability = does it recover from failure and keep working over time

Vertical vs Horizontal scaling Vertical = a bigger/smaller single resource (scale up/down); horizontal = more/fewer instances (scale out/in)

Agility vs Elasticity Agility = how fast you can deploy/change anything; elasticity = automatic capacity matching specifically

Keep these distinctions sharp: a question can offer two correct-sounding benefit terms, and only the precise match earns the point.