AZ-900 Exam Cram: Describe Cloud Computing

This cram sheet focuses on the foundational concepts of cloud computing, the shared responsibility model, and cloud deployment models required for the Microsoft Azure Fundamentals (AZ-900) exam.

Topic Weighting

[!IMPORTANT] This section is the foundation for the entire exam. Understanding who is responsible for what is a frequent source of exam questions.

Key Concepts Summary

• Cloud Computing: The delivery of computing services—including servers, storage, databases, networking, software, and analytics—over the internet ("the cloud").
• Shared Responsibility Model: A framework that divides security and management tasks between the cloud provider (Microsoft) and the customer.
• Consumption-Based Model: Users pay only for the resources they use. This shifts costs from Capital Expenditure (CapEx) to Operational Expenditure (OpEx).
• Cloud Models:
  • Public: Services offered over the public internet and available to anyone who wants to purchase them. Hardware is shared (multi-tenant).
  • Private: Computing resources used exclusively by one business or organization. Can be physically located at an on-site datacenter or hosted by a third-party provider.
  • Hybrid: A computing environment that combines a public cloud and a private cloud, allowing data and applications to be shared between them.
• Serverless: The abstraction of servers, infrastructure, and operating systems. The cloud provider automatically manages the code execution environment.

Shared Responsibility Visualization

Common Pitfalls

• "Cloud = No Maintenance" Myth: Many believe moving to the cloud removes all IT burden. In reality, customers are always responsible for their data, identities, and devices regardless of the service model.
• CapEx vs. OpEx Confusion: Remember that CapEx involves upfront spending on physical infrastructure, while OpEx is the ongoing cost for a service or product. Cloud is primarily OpEx.
• Hybrid Cloud Misconception: A hybrid cloud is not just "using two clouds"; it specifically requires connectivity and data portability between a private (on-premises) and public cloud.
• Private Cloud Location: A private cloud does not have to be on-premises; it just has to be dedicated to a single tenant.

Mnemonics / Memory Triggers

• The "D.I.A." Rule: In the Shared Responsibility Model, the Customer ALWAYS owns Data, Identity, and Access (Endpoints).
• P.P.H. (Cloud Models):
  • Public = Shared (Public Bus)
  • Private = Single (Own Car)
  • Hybrid = Integrated (Park & Ride/Commuter Train)
• Pay-as-you-GO: The consumption-based model is like a utility bill (Electricity); you don't buy the power plant, you just pay for the watts you use.

Formula / Concept Sheet

Cloud Model Comparison

Expenditure Types

Practice Set

1. Which cloud model is used by a company that provides resources to the general public over the internet?
   • Answer: Public Cloud.
2. True or False: In a SaaS model, the cloud provider is responsible for managing the physical network.
   • Answer: True (The provider manages the infrastructure in all cloud models).
3. Identify the cost type: Purchasing a new server rack for an on-premises datacenter.
   • Answer: Capital Expenditure (CapEx).
4. In the Shared Responsibility Model, which of the following is the customer ALWAYS responsible for?
   • A. Physical Hardware
   • B. Data and Content
   • C. Hypervisor
   • Answer: B. Data and Content.
5. Which concept describes the ability to pay only for the resources you use without upfront costs?
   • Answer: Consumption-based model.

[!TIP] When you see "Serverless" on the exam, think Azure Functions or Logic Apps. It means you don't manage the underlying VM or OS at all.