Ultimate Guide to Cloud Computing Concepts for AZ-900 Certification (2025 Update)

Introduction to Cloud Computing for AZ-900

There are different cloud computing concepts are required for AZ 900 Certification. The overall weightage of this is about 20%

Core Characteristics of Cloud Computing

Scalability

Scalability in cloud computing refers to the ability to increase or decrease resources based on demand.

• Vertical Scaling: Adding more power (CPU, memory) to an existing machine.
• Horizontal Scaling: Adding more instances of machines to handle load.

Elasticity

Elasticity is the capability to automatically scale resources up or down based on usage patterns. It ensures optimal performance without manual intervention.

Agility

Cloud agility allows businesses to respond quickly to changes. Resources can be provisioned or de-provisioned in seconds, unlike traditional systems that take days or weeks.

Agility is the ability to allocate and deallocate(Scale) resources quickly

Cloud	On-Prem
Seconds	Days
Minutes	Weeks
Hours	Months

Fault Tolerance

A fault-tolerant cloud system continues to operate even when components fail. This ensures continuous availability and minimal service disruption.

Disaster Recovery

Disaster recovery is the process of restoring services after an outage or disaster, whether due to hardware failure, human error, or natural calamities.

High Availability

High availability ensures maximum uptime.
Formula: Availability = Uptime / (Uptime + Downtime)
Cloud systems are designed for redundancy and failover to keep services accessible.

Understanding Cloud Economics: CapEx vs OpEx

Capital Expenditure (CapEx)

Key Characteristics

• Invests in physical infrastructure
• Requires significant upfront costs
• High maintenance and staffing requirements

Operational Expenditure (OpEx)

Key Characteristics

• Pay-as-you-go model
• Minimal upfront investment
• Reduced maintenance and support needs

Differences

Characteristics	CapEx	OpEx
Upfront cost	Significant	None
Ongoing Cost	Low	Based on Usage
Tax Deduction	Over time	Same year
Early Termination	No	Anytime
Maintenance	Significant	Low
Value over time	Lowers	No change

Consumption-Based Pricing Model

Key Characteristics

• No upfront investment
• Charges based on actual usage
• Services billed per compute, storage, and network usage
• Highly granular billing metrics

Cloud Service Models: IaaS, PaaS, and SaaS

Infrastructure as a Service (IaaS)

You manage: OS, middleware, runtime, data, applications
Provider manages: Networking, storage, servers, virtualization
Use Cases: VM hosting, test environments, backups

Platform as a Service (PaaS)

You manage: Applications and data
Provider manages: Infrastructure and platform
Use Cases: App development, analytics, BI tools

Software as a Service (SaaS)

Provider manages everything – from hardware to application
Use Cases: Email, CRM, productivity tools

Infrastructure → Storage – Networking – Server – Virtualization 

Cloud Deployment Models

Public Cloud

Key Characteristics

• Everything runs in the cloud provider hardware.
• No local hardware
• Some Services share hardware with other customers

Advantages and Disadvantages

Advantages	Disadvantages
No Capex	Security & Compliance
High availability & agility	Ownership
Security & Compliance	Specific scenarios with unique business requirements
No hardware maintenance
No deep technical skills required

Private Cloud

Key Characteristics 

• Everything runs on your data center.
• Self-service should be provided
• You maintain the hardware

Advantages	Disadvantages
Can support any scenario	Initial Capex
Control over security	Limited Agility
Can meet any security & compliance & requirements	IT skills expertise are mandatory

Hybrid Cloud 

Key Characteristics 

• Combines public & private clouds
• Great Flexibility

Advantages	Disadvantages
Great flexibility	Can be more expensive
Run legacy apps in a private cloud	Complicated to manage
Utilize existing infrastructure	IT Skills & Expertise are mandatory
Meet any security requirements

Azure Geographies, Regions, and Availability Zones

Data Centers

Key characteristics 

• Physical facility
• Hosting for a group of networked servers
• Own power, cooling & networking infrastructure.

Azure Regions

Key characteristics 

• Geographical area on the planet
• One or usually more data centers connected with a low-latency network(< 2 milliseconds)
• Location for your services 
• Some Services are available only in certain regions
• Some services are global and, as such, are not assigned/deployed in a specific region
• Globally available with 50+ regions
• Special government regions(US DOD Central, US Gov Virginia, etc)
• Special partnered regions(China East, China North)

Availability Zones

Key Characteristics

• Regional feature
• Grouping of physically separate facilities
• Designed to protect from data center failures
• If the zone goes down, others continue working
• Zonal Services (Virtual Machines Disks, etc)
• Not all regions are supported
• The supported region has three or more zones
• A zone is one or more data centers

Region Pairs

Key Characteristics

• Each region is paired with another region, making it a region pair
• Region pairs are static and cannot be chosen
• Each pair resides within the same Geography
  • The exception is Brazil’s South
• Physical isolation with at least 300 miles distance(when possible)
• Some Services have platform-provided replication
• Planned updates across the pairs
• Data residency is maintained for disaster recovery

Region Pair A	Region Pair B
East US	West US
UK West	UK South
North Europe(Ireland)	West Europe(Netherlands)
East Asia(Hong Kong)	Southeast Asia(Singapore)

Geographies

Key Characteristics

• Discrete market
• Typically contains two or more regions
• Ensures data residency, sovereignty, resiliency, and compliance requirements are met
• Fault-tolerant to protect from region-wide failures
• Broken up into areas
  • Americas,
  • Europe
  • Asia Pacific
  • Middle East and Africa
• Each region belongs only to one Geography

Azure Resource Structure

Resources

Key Characteristics

• Objects  used to manage services in Azure
• Represents the service lifecycle
• Every resource is a JSON Template
• Saved as JSON Definition

Resource Groups

Key Characteristics

• Grouping of resources 
• Holds logically related resources
• Organizing by –
  • Type
  • Lifecycle(app,environment)
  • Department
  • Billing, Location, or a combination of those

• Each resource must be and only one resource group
• Resource groups have their location assigned 
• Resources in the resource groups can reside in different locations
• Resources can be moved between the resource groups 
• Resource groups can’t be nested
• Organize based on your organization’s needs, but consider
  • Billing
  • Security and access management
  • Application Lifecycle

Azure Resource Manager

Key Characteristics

• Management Layer for all resources and resource groups
• Unified language