Cloud Computing Fundamentals

This module introduces the foundational concepts of cloud computing. We'll explore what it means to move from traditional on-premises infrastructure to the cloud, the financial shift from CapEx to OpEx, and the essential benefits that drive cloud adoption. You will also learn the differences between the core service models (IaaS, PaaS, SaaS) and deployment models (Public, Private, Hybrid).

What is Cloud Computing?

Cloud computing is the delivery of computing services: servers, storage, databases, networking, software, and analytics: over the internet. Instead of owning and maintaining your own physical hardware in a data center, you can access these capabilities on demand from a cloud provider like Microsoft and pay only for what you use.

In Plain English

Think of it like electricity. You do not build a power station to power your home; you plug into the grid and pay for what you use. Cloud computing works the same way for computing power.

The Shift from On-Premises to Cloud

Before the cloud, companies had to buy physical servers, maintain data centers, and hire staff to manage it all. This required enormous upfront investment and long-term capacity planning. The cloud model offers a fundamentally different approach.

Aspect	On-Premises (Traditional)	Cloud (Azure)
Initial Cost	Very high: buy servers, racks, cooling	None: pay as you consume
Scalability	Limited by physical hardware purchased	Effectively unlimited: scale in minutes
Speed to Deploy	Weeks or months	Minutes or hours
Maintenance	Your IT team responsible for everything	Microsoft handles the physical infrastructure
Disaster Recovery	Expensive to set up and test	Built-in redundancy options
Geographic Reach	Only where you have physical data centers	60+ regions worldwide instantly
Cost Model	Capital Expenditure (CapEx)	Operational Expenditure (OpEx)

CapEx vs. OpEx: The Financial Shift

Understanding the financial models is a critical concept for the AZ-900 exam and for making real-world business decisions.

Category	Capital Expenditure (CapEx)	Operational Expenditure (OpEx)
Definition	Large upfront investment in physical assets	Ongoing spending on services as needed
Payment	One-time or infrequent large purchase	Pay-as-you-go, monthly, per-use
Accounting	Depreciated over several years	Fully expensed in the period incurred
Flexibility	Low: committed to assets regardless of use	High: stop paying when you stop using
Examples	Buying servers, building a data center	Azure subscription, SaaS fees, utilities
Cloud Fit	On-premises infrastructure	Cloud computing

Exam Tip

Cloud computing primarily uses an OpEx model. You pay for what you use, when you use it, with no upfront commitment to physical hardware.

Seven Key Benefits of Cloud Computing

Microsoft highlights seven core benefits that the cloud provides to businesses.

Benefit	What It Means	Real-World Example
High Availability	Apps stay running even when components fail.	Your website stays online even if one server has a hardware fault.
Scalability	Add or remove resources based on demand.	An e-commerce site handles Black Friday traffic without crashing.
Reliability	The system can recover from failures automatically.	If a data center loses power, services in another take over smoothly.
Predictability	Consistent performance and costs you can plan for.	You experience the same response times and billing patterns month over month.
Security	Built-in tools to protect data and applications.	You get encryption, firewalls, and threat detection without building them yourself.
Governance	Enforce policies across all your cloud resources.	You can ensure no one creates resources in unapproved geographic regions.
Manageability	Automate and manage resources with ease.	You can auto-scale servers at night or receive alerts before issues affect users.

Cloud Service Models: IaaS, PaaS, SaaS

All cloud services fit into one of three models, defined by who manages what. This is often called the "Shared Responsibility Model".

	IaaS	PaaS	SaaS
Full Name	Infrastructure as a Service	Platform as a Service	Software as a Service
You Manage	OS, middleware, runtime, apps, data	Application code and data only	Nothing: just use the software
Provider Manages	Hardware, networking, virtualization	Everything up to the runtime	Everything end to end
Typical Users	System administrators, IT teams	Developers building applications	End users and business teams
Azure Examples	Azure VMs, Azure Storage	Azure App Service, Azure SQL Database	Microsoft 365, Dynamics 365
Best For	Maximum control, legacy app migration	Building and deploying apps fast	Ready-to-use business applications

In Plain English

IaaS is like renting a kitchen: you bring your own ingredients and cook. PaaS is like a meal-kit service: they provide ingredients and recipes, you cook. SaaS is like a restaurant: you just show up and eat.

Cloud Deployment Models

This defines where the cloud infrastructure lives and who can access it.

Model	Who Owns It	Who Can Access It	Strengths	Typical Use Cases
Public Cloud	Cloud provider (e.g., Microsoft)	Anyone over the internet	Low cost, instant scale, no maintenance	Startups, web apps, development & testing.
Private Cloud	Your organization	Only your organization	Maximum control, security, and isolation	Highly regulated industries, sensitive data.
Hybrid Cloud	Both your org and a provider	A controlled mix of both	Flexibility, data sovereignty, gradual migration	Keeping sensitive data on-prem while using public cloud for scale.
Multi-Cloud	Multiple cloud providers	Depends on configuration	Avoid vendor lock-in, use best-of-breed services	Enterprise resilience and feature optimization strategies.

Cloud Pricing Models in Azure

Azure offers several pricing models so you can match how you pay to how you actually use resources. Choosing the right combination is one of the highest-impact ways to control cloud costs.

Pricing Model	How It Works	Savings vs. Pay-As-You-Go	Best For
Pay-As-You-Go	Pay per second/minute for what you use	Baseline (0%)	Variable or unpredictable workloads
Azure Reservations	Commit to 1 or 3 years upfront or monthly	Up to 72%	Steady, predictable workloads
Azure Spot Instances	Use spare Microsoft capacity at a deep discount	Up to 90%	Interruptible batch jobs only
Azure Hybrid Benefit	Apply existing on-prem licenses to Azure	Up to 40%	Customers with existing Windows/SQL licenses

Exam Tip

Spot Instances are NOT suitable for production environments. Azure can reclaim them with little notice. Only use them for work that can be safely interrupted.

Serverless Computing

Serverless does NOT mean there are no servers: it means you never think about servers. The cloud provider handles all infrastructure automatically. You write code, deploy it, and pay only when it runs.

Azure Serverless Service	What It Does	Triggered By
Azure Functions	Run individual code functions on demand	HTTP requests, timers, queue messages, events
Azure Logic Apps	Automate workflows between services visually	Events, schedules, or manual triggers
Azure Event Grid	Route events from Azure services to handlers	Resource changes, custom events

In Plain English

Azure AI services like Cognitive Services APIs are essentially serverless: you call an API, it runs, you pay per call. No servers to manage. This is the same model you will use throughout your Azure AI journey.