Chapter 05 — Cloud Deployment Models

What are Cloud Deployment Models?

A cloud deployment model defines where the cloud infrastructure lives and who manages it. It determines the ownership, location, and accessibility of the cloud environment.

There are three main cloud deployment models:

Public Cloud  →  Resources owned and operated by a third-party provider
Private Cloud →  Resources owned and used by a single organization
Hybrid Cloud  →  Combination of public and private cloud

AZ-900 also touches on a newer concept: Multi-Cloud.

1. Public Cloud

What Is It?

In a public cloud, computing resources (servers, storage, networking) are owned and operated by a third-party cloud provider — such as Microsoft Azure — and delivered over the internet.

Multiple organizations share the same physical infrastructure, but each customer's data and workloads are logically isolated and kept private.

Key Characteristics

Advantages

• No upfront capital expenditure (CapEx)

• Pay only for what you use (OpEx)

• Massive scale and global reach

• No hardware maintenance burden

• Access from anywhere

Disadvantages

• Less control over the underlying infrastructure

• Internet dependency — outages can affect access

• May not meet strict data sovereignty or compliance needs

Azure as Public Cloud

Microsoft Azure is a public cloud platform — you access resources through the Azure portal, CLI, or APIs over the internet, and Microsoft owns and operates all the physical data centers.

Best For

• Startups and small businesses with no IT budget for hardware

• Websites, web apps, and APIs with variable traffic

• Development, testing, and non-sensitive workloads

• Organizations wanting to innovate without infrastructure burden

2. Private Cloud

What Is It?

A private cloud is a cloud environment used exclusively by one organization. The infrastructure may be:

• Located on-premises in the organization's own data center

• Hosted by a third-party provider but dedicated solely to that organization

Key Characteristics

Advantages

• Full control over hardware, software, and data

• Higher security and privacy — no shared infrastructure

• Meets strict regulatory and compliance requirements

• Customizable to specific organizational needs

Disadvantages

• High upfront cost (CapEx)

• Requires IT staff to manage infrastructure

• Limited scalability compared to public cloud

• Slower provisioning

Best For

• Government agencies with classified data

• Financial institutions with strict data residency laws

• Healthcare organizations with sensitive patient records (HIPAA)

• Large enterprises with existing data centers they want to modernize

3. Hybrid Cloud

What Is It?

A hybrid cloud combines public and private cloud environments, allowing data and applications to move between them. Organizations use this model to get the best of both worlds.

Private Cloud (On-Premises)  ←──────────→  Public Cloud (Azure)
         │                   Secure Link           │
         │                (VPN / ExpressRoute)      │
         │                                          │
  Sensitive data                              Burst capacity
  Legacy systems                              Web-facing apps
  Compliance workloads                        Dev/test environments

Key Characteristics

Advantages

• Flexibility — keep sensitive data on-premises, burst to cloud when needed

• Cost optimization — use cloud only for variable workloads

• Compliance — store regulated data privately while using cloud for other workloads

• Gradual cloud migration path

Disadvantages

• More complex to set up and manage

• Requires secure connectivity (VPN or ExpressRoute)

• Potential latency between private and public environments

• Requires expertise in both environments

Best For

• Organizations with existing on-premises investments

• Companies with regulatory requirements for certain data

• Businesses with seasonal workload spikes (e.g., retail during holidays)

• Enterprises undergoing gradual cloud migration

4. Multi-Cloud

What Is It?

Multi-cloud means using cloud services from more than one cloud provider simultaneously — for example, using Azure for compute and AWS for a specific AI service.

  Azure (Microsoft)  +  AWS (Amazon)  +  Google Cloud
       │                    │                  │
  Your workloads distributed across multiple providers

Why Organizations Use Multi-Cloud

• Avoid vendor lock-in

• Use best-in-class services from each provider

• Meet different regional requirements

• Redundancy and risk mitigation

Note: Multi-cloud management tools like Azure Arc allow you to manage resources across multiple clouds from a single control plane.

Deployment Models Comparison

Real-World Scenarios

Scenario 1 — A hospital

Model: Hybrid Cloud

• Patient records stay on-premises (private cloud) due to HIPAA compliance

• Administrative tools and website run on Azure (public cloud)

• VPN connects both environments securely

Scenario 2 — A fast-growing e-commerce startup

Model: Public Cloud

• No money for hardware

• Needs to scale during sales events

• All workloads on Azure

Scenario 3 — A national defense agency

Model: Private Cloud

• Classified data cannot leave government-controlled facilities

• Full control and custom security required

Quick Recap

Public Cloud  →  Third-party owned, shared infra, pay-as-you-go
Private Cloud →  Your own exclusive environment, full control
Hybrid Cloud  →  Mix of both — best of both worlds
Multi-Cloud   →  Using multiple cloud providers simultaneously

Most organizations use Hybrid Cloud in practice.

Official References

• Cloud deployment models — Microsoft Learn

• What is a public cloud? — Microsoft Azure

• What is a private cloud? — Microsoft Azure

• What is a hybrid cloud? — Microsoft Azure

Next Chapter → Chapter 06: The Shared Responsibility Model