AZ-900 Study Notes

Comprehensive study notes covering all Azure Fundamentals exam domains with detailed explanations, tables, and exam tips.

Microsoft Azure Fundamentals Study Notes

Cloud Computing Fundamentals

Essential cloud computing concepts for AZ-900

Domain Weight

This domain represents 25-30% of the exam. Focus on understanding cloud concepts and Azure's value proposition.

What is Cloud Computing?

Definition: Delivery of computing services (servers, storage, databases, networking, software) over the internet
On-Demand: Provision resources as needed without upfront investment
Scalability: Increase or decrease resources based on demand
Elasticity: Automatically scale resources in response to demand
Pay-as-you-go: Only pay for resources you actually consume

CapEx vs OpEx

Capital Expenditure (CapEx)	Operational Expenditure (OpEx)
Upfront investment in physical infrastructure	Pay for services as you use them
Depreciated over time	Deducted in same billing period
Requires accurate forecasting	Flexible, adjust as needs change
High initial cost	Lower initial cost
You own the infrastructure	Provider owns infrastructure

Consumption-Based Model

Cloud computing uses a consumption-based model where you only pay for what you use. This provides better cost prediction and eliminates waste from overprovisioned resources.

Cloud Service Models

IaaS, PaaS, and SaaS explained

Service Model Comparison

Model	Description	You Manage	Provider Manages	Azure Examples
IaaS	Infrastructure as a Service	OS, runtime, apps, data	Hardware, networking, virtualization	VMs, VNets, Storage
PaaS	Platform as a Service	Apps and data only	Everything else including OS	App Service, Azure SQL, Functions
SaaS	Software as a Service	Just use the application	Everything	Microsoft 365, Dynamics 365

Shared Responsibility Model

Always Your Responsibility

Information and data, devices, accounts and identities

Always Azure Responsibility

Physical datacenter, physical network, physical hosts

Varies by Service Model

Operating system, network controls, applications, identity infrastructure

Exam Tip

Know what you manage vs what Azure manages for each service model. IaaS = most customer responsibility, SaaS = least customer responsibility.

Cloud Deployment Models

Public, Private, and Hybrid Cloud

Deployment Model Comparison

Model	Description	Advantages	Disadvantages
Public Cloud	Services offered over public internet, owned by cloud provider	No CapEx, agility, pay-as-you-go, no maintenance	Less control, security concerns, compliance challenges
Private Cloud	Computing resources used exclusively by one organization	More control, customization, legacy support	CapEx required, limited scalability, maintenance burden
Hybrid Cloud	Combines public and private clouds	Flexibility, compliance options, gradual migration	Complexity, integration challenges, cost management

Hybrid Cloud Use Cases

Cloud Bursting: Use public cloud for peak demand while running baseline on-premises
Compliance: Keep sensitive data on-premises while using cloud for other workloads
Gradual Migration: Move workloads to cloud incrementally
Disaster Recovery: Use cloud as backup site for on-premises infrastructure

Benefits of Cloud Computing

Key advantages of using cloud services

Core Benefits

High Availability

Resources available when needed, typically expressed as percentage uptime (99.9% = 8.76 hours downtime/year)

Scalability

Vertical (scale up/down) - add CPU/RAM. Horizontal (scale out/in) - add/remove instances

Elasticity

Automatically scale resources based on actual demand in real-time

Reliability

Decentralized design enables deployment in multiple regions for fault tolerance

Predictability

Predictable performance through autoscaling and load balancing; predictable costs through tracking and forecasting

Security

Cloud providers offer security tools and features; customers retain control over implementation

Governance

Templates and auditing help ensure resources comply with corporate standards

Manageability

Manage through portal, CLI, APIs, or PowerShell; autoscaling and template-based deployment

SLA (Service Level Agreement)

Azure commits to specific uptime percentages for each service. Higher availability = more complex architecture (multiple regions, availability zones). Know that 99.99% (four 9s) allows only ~52 minutes of downtime per year.

Capital Expenditure (CapEx)

Operational Expenditure (OpEx)

Upfront investment in physical infrastructure

Pay for services as you use them

Depreciated over time

Deducted in same billing period

Requires accurate forecasting

Flexible, adjust as needs change

High initial cost

Lower initial cost

You own the infrastructure

Provider owns infrastructure

Model

Description

You Manage

Provider Manages

Azure Examples

IaaS

Infrastructure as a Service

OS, runtime, apps, data

Hardware, networking, virtualization

VMs, VNets, Storage

PaaS

Platform as a Service

Apps and data only

Everything else including OS

App Service, Azure SQL, Functions

SaaS

Software as a Service

Just use the application

Everything

Microsoft 365, Dynamics 365

Model

Description

Advantages

Disadvantages

Public Cloud

Services offered over public internet, owned by cloud provider

No CapEx, agility, pay-as-you-go, no maintenance

Less control, security concerns, compliance challenges

Private Cloud

Computing resources used exclusively by one organization

More control, customization, legacy support

CapEx required, limited scalability, maintenance burden

Hybrid Cloud

Combines public and private clouds

Flexibility, compliance options, gradual migration

Complexity, integration challenges, cost management

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AZ-900 Study Notes

Microsoft Azure Fundamentals Study Notes

Domain Weight

What is Cloud Computing?

CapEx vs OpEx

Consumption-Based Model

Service Model Comparison

Shared Responsibility Model

Always Your Responsibility

Always Azure Responsibility

Varies by Service Model

Exam Tip

Deployment Model Comparison

Hybrid Cloud Use Cases

Core Benefits

High Availability

Scalability

Elasticity

Reliability

Predictability

Security

Governance

Manageability

SLA (Service Level Agreement)

AZ-900 Study Notes

Microsoft Azure Fundamentals Study Notes

Domain Weight

What is Cloud Computing?

CapEx vs OpEx

Consumption-Based Model

Service Model Comparison

Shared Responsibility Model

Always Your Responsibility

Always Azure Responsibility

Varies by Service Model

Exam Tip

Deployment Model Comparison

Hybrid Cloud Use Cases

Core Benefits

High Availability

Scalability

Elasticity

Reliability

Predictability

Security

Governance

Manageability

SLA (Service Level Agreement)