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Identify Appropriate Use Cases for Each Cloud Model

az-900•mixed•

Cloud concepts

Identify Appropriate Use Cases for Each Cloud Model

Short Summary

Public, private, and hybrid cloud deployment models fit different constraints. In this lesson, you’ll learn simple rules of thumb for choosing a model based on scaling needs, cost, control, compliance, and existing on-premises systems. You’ll also practice explaining your choice clearly from a short scenario.

Learning Objectives

By the end of this lesson, you will be able to:

  • Match a workload to public, private, or hybrid cloud based on business and technical requirements.
  • Differentiate cloud deployment models (public/private/hybrid) from cloud service models (Infrastructure as a Service (IaaS), Platform as a Service (PaaS), Software as a Service (SaaS)).
  • Explain common trade-offs (cost, control, compliance, and operational effort) across the three cloud models.
  • Recognize when hybrid cloud is a deliberate long-term approach, not just a migration step.
  • Justify your choice using common scenario clues (for example, “must stay on-premises,” “single-tenant/dedicated,” or “unpredictable spikes”).

Core Concepts

Cloud deployment models (sometimes called “cloud models”) describe where a cloud environment runs and who owns/operates it. For AZ-900, focus on:

  • Public cloud
  • Private cloud
  • Hybrid cloud

Public cloud

A public cloud is owned and operated by a cloud provider. Resources (like compute, storage, and networking) are typically shared across multiple customers (multitenant) and accessed over a network (often the internet).

Public cloud is usually a strong fit when you want:

  • Fast provisioning and quick experimentation
  • Easy scaling up/down with demand
  • Lower upfront infrastructure cost (pay-as-you-go vs buying hardware)

Private cloud

A private cloud is a cloud environment dedicated to a single organization (single-tenant). It can be hosted in your own datacenter (on-premises) or hosted by a third party in a dedicated environment.

Private cloud is often chosen when you need:

  • Strong isolation or dedicated infrastructure
  • Greater control over configuration and customization
  • Policies or requirements that push you toward dedicated environments

Important nuance: an on-premises datacenter becomes “private cloud” when it adds cloud-like capabilities such as automation and self-service provisioning. Without those, it’s just traditional infrastructure.

Hybrid cloud

A hybrid cloud combines public cloud services with private cloud and/or on-premises infrastructure in a connected way. The goal is to use the “best location” for each workload or dataset, based on constraints.

Hybrid cloud is common when:

  • Some workloads or data must remain on-premises or in a dedicated environment
  • You still want public cloud services for other parts (dev/test, analytics, web apps, burst capacity)
  • You need integration between environments (data and apps moving between them)

A quick rule of thumb

There is no single “best” model. Pick the model that best matches the constraints:

  • Public cloud: prioritize speed, elasticity, and low upfront infrastructure.
  • Private cloud: prioritize dedicated environments and stronger control expectations.
  • Hybrid cloud: prioritize connected environments because requirements force mixed placement.

Don’t confuse deployment models with service models

Deployment models answer: Where does it run and who operates it? (public/private/hybrid)

Service models answer: How much does the provider manage? (IaaS/PaaS/SaaS)

A scenario can mention IaaS/PaaS/SaaS, but you still decide whether the workload is best placed in a public, private, or hybrid environment.

Practical Understanding

Practical Situation 1: “Demand is unpredictable and we want to avoid upfront infrastructure”

A startup is launching an internet-facing app. They expect traffic spikes and want to scale quickly without buying servers up front.

How to think about it: This is a classic public cloud fit: fast provisioning, pay-as-you-go costs, and elasticity for unpredictable demand.

Common misunderstanding: “Internet-facing automatically means public cloud.” Not always—dedicated isolation, strict data-location rules, or “must stay on-premises” constraints can change the answer.

Practical Situation 2: “We require a dedicated (single-tenant) environment and tight control”

A healthcare organization says patient workloads must run in a dedicated environment and they must tightly control data location and access.

How to think about it: “Dedicated / single-tenant required” is a strong signal for private cloud. The scenario is prioritizing isolation and control over shared infrastructure.

Common misunderstanding: “Private cloud means on-premises only.” Private cloud can be on-premises or hosted elsewhere; the key is that it’s dedicated to one organization.

Practical Situation 3: “Some data must stay on-prem, but we also want cloud services”

A financial organization has critical legacy systems on-premises. Regulations require sensitive data to remain on-premises, but they want to build new apps and dev/test in the cloud.

How to think about it: This points to hybrid cloud: keep regulated data and legacy systems on-premises while using public cloud services where allowed.

Common misunderstanding: “Hybrid is only a temporary migration stage.” Hybrid can be long-term by design if requirements keep demanding mixed placement.

Practical Situation 4: “Cloud analytics must access on-prem data without disrupting production”

A manufacturing company relies on on-prem systems that cannot be disrupted. They want cloud-based analytics and machine learning that can access on-prem data.

How to think about it: This is another hybrid cloud pattern: keep critical systems on-prem while connecting them to public cloud services that add new capabilities.

Common misunderstanding: “Public cloud can’t work with on-premises.” It can—when you connect the environments, the deployment model describing that setup is hybrid.

Common Pitfalls

  • Mistake: Assuming public cloud is always the right answer because it is “the cloud.” Correction: Match the model to constraints; compliance, isolation, latency, and “must stay on-premises” requirements can rule out public-only.

  • Mistake: Thinking private cloud simply means “on-premises hardware.” Correction: Private cloud is a dedicated environment for one organization with cloud-like management (automation, self-service, elasticity), whether hosted on-premises or by a third party.

  • Mistake: Treating hybrid cloud as a synonym for “migration.” Correction: Hybrid is a connected, mixed-environment strategy and can be permanent if requirements demand it.

  • Mistake: Ignoring the operational trade-offs of private and hybrid models. Correction: More control and isolation often come with more complexity, skills, and cost to operate.

  • Mistake: Confusing deployment models (public/private/hybrid) with service models (IaaS/PaaS/SaaS). Correction: Deployment models describe placement/ownership; service models describe how much of the stack is managed by the provider.

Check Your Understanding

  1. Define public cloud, private cloud, and hybrid cloud in one sentence each using the words “shared,” “dedicated,” and “connected.”
  2. You see: “Some workloads must stay in our datacenter, but we want cloud analytics.” Which model fits, and what single phrase in the scenario drives your choice?
  3. List three scenario clues that strongly point to private cloud, and explain what each clue is really asking for.
  4. Pick a workload you know (website, internal system, mobile backend). Describe what must be true for public cloud to be the best fit.
  5. Explain the difference between “hybrid cloud” and “we’re migrating to the cloud” in your own words.

Further Reading