This chapter covers the three cloud deployment models — public, private, and hybrid — and how they differ in terms of control, ownership, and use case. AZ-900 tests this under objective 1.3.
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A simple way to picture Public, Private, and Hybrid Cloud
A private garden behind your house is entirely yours — you control who enters and how it's used, but you're also solely responsible for maintaining it. A public park is open and shared by everyone in the city, maintained by the city itself, and you have no exclusive control over it. A community garden plot sits in between: part of a larger shared space, but with a section reserved and managed specifically for you, connected to the public area around it. These map to the three cloud deployment models: a private cloud is like the private garden (dedicated, exclusive), a public cloud is like the public park (shared infrastructure, open to many), and a hybrid cloud is like the community plot — a private section connected to and working alongside a larger shared space.
Public cloud
In a public cloud, infrastructure is owned and operated by a cloud provider (like Microsoft, for Azure) and shared across many customers, though each customer's resources and data remain logically isolated from others. This is the most common model for organizations that want to avoid owning physical infrastructure entirely.
Private cloud
A private cloud is dedicated to a single organization — the infrastructure may be hosted on-premises or by a third party, but it isn't shared with other customers. This gives more control and can help meet specific regulatory or security requirements, at the cost of the organization taking on more responsibility for managing that infrastructure.
Hybrid cloud
A hybrid cloud combines public and private cloud environments, allowing data and applications to be shared between them. This lets an organization keep certain sensitive workloads in a private environment while still taking advantage of the scalability and services of the public cloud for other workloads.
Choosing between them
The right deployment model depends on factors like regulatory requirements, existing infrastructure investments, and how much control an organization needs versus how much operational burden it wants to avoid. There's no universally "best" model — it depends on the specific organization's needs and constraints.
Assess regulatory and control requirements
Some industries or regions have requirements that push organizations toward private or hybrid models for certain data, while others are comfortable fully adopting public cloud.
Evaluate existing infrastructure investments
An organization with significant existing on-premises infrastructure might choose hybrid cloud to gradually extend into the public cloud rather than migrating everything at once.
Consider scalability needs
Public cloud generally offers the most flexible scalability, since it draws on a provider's large shared infrastructure pool rather than a fixed private capacity.
Decide per-workload, not just organization-wide
Many organizations don't pick a single deployment model for everything — they choose the right model for each specific workload based on its individual requirements.
A healthcare organization with strict data-residency and regulatory requirements keeps patient records in a private cloud environment, while using public cloud services for less sensitive workloads like its public website and customer-facing applications — a hybrid approach.
A startup with no existing infrastructure and no special regulatory constraints goes fully public cloud from the start, since there's no legacy investment to account for and public cloud offers the fastest path to scalable infrastructure. Organizations sometimes assume they must pick one deployment model company-wide, when in practice most large organizations mix models across different workloads based on each one's specific needs.
Objective 1.3 expects candidates to distinguish between public, private, and hybrid cloud, and to recognize which model fits a described scenario.
A common wrong answer is assuming private cloud always means "on-premises" — a private cloud can be hosted on-premises or by a third party, as long as the infrastructure is dedicated to a single organization rather than shared. Another common trap is assuming hybrid cloud is simply "using two different providers" — hybrid specifically refers to combining public and private environments, not multiple public cloud providers (that's a related but different concept: multi-cloud).
Stable terms: public cloud, private cloud, hybrid cloud. Knowing what distinguishes each — shared vs. dedicated infrastructure, and whether public and private environments are combined — is the core exam-relevant distinction.
Memory trick: public = shared infrastructure, provider-owned. Private = dedicated infrastructure, single organization. Hybrid = both, connected together.
Public cloud infrastructure is shared across many customers and owned by the provider.
Private cloud infrastructure is dedicated to a single organization, whether hosted on-premises or by a third party.
Hybrid cloud combines public and private environments, letting data and applications move between them.
Deployment model choice is often made per-workload, not as a single organization-wide decision.
These come up on the exam all the time. Here's how to tell them apart.
Public Cloud
Infrastructure shared across many customers
Owned and operated by the provider
Generally the most scalable and cost-flexible
Less direct control over underlying infrastructure
Private Cloud
Infrastructure dedicated to a single organization
Can be hosted on-premises or by a third party
More control, often used for specific compliance needs
Organization takes on more management responsibility
Mistake
Private cloud always means the infrastructure is physically on-premises.
Correct
Private cloud means the infrastructure is dedicated to a single organization — it can be hosted on-premises or by a third party, as long as it isn't shared with other customers.
Mistake
Hybrid cloud means using two different cloud providers.
Correct
Hybrid cloud specifically means combining public and private cloud environments. Using multiple public cloud providers together is a related but different concept, usually called multi-cloud.
Mistake
Organizations must choose one deployment model for everything.
Correct
Many organizations use different deployment models for different workloads, based on each workload's specific requirements, rather than committing to a single model company-wide.
They're related but not identical — private cloud specifically means infrastructure dedicated to a single organization, which can be hosted on-premises or by a third-party provider. Traditional on-premises infrastructure, without any cloud-style self-service or elasticity, isn't automatically the same as a private cloud.
No. Hybrid cloud refers to combining public and private cloud environments together. Multi-cloud refers to using multiple public cloud providers. They're related concepts but describe different things.
It depends on factors like regulatory requirements, existing infrastructure, and scalability needs — there's no universally best option. Many organizations use different deployment models for different workloads rather than picking just one.
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