AZ-900: Describe Cloud Concepts

Adil Shehzad
11 min readFeb 9, 2021

The Microsoft Azure Az-900 Training is Absolutely Free and Resources are also totally free.

Describe the benefits and considerations of using cloud services

High Availability

Refer to how long your service is up and running without interruptions. high Availability or highly available refers to a source that's up and running for a long period of time. While Surfing on any website an error occurs 503 which means service is not available.


Refer to systems that operate during abnormal conditions such as Natural diaster, system maintenance, both planned or unplanned, software upgrade, or security patches. or threats like usually traffic because of DDOS attacks.


Refer to the time it takes data to travel over the network. Latency is measured in milliseconds.


Refer to the maximum data which travels throughput the capacity of the network. Bandwidth can be measured in bits, megabits, or gigabits per second.


Refer to the logical group of two or more virtual machines(VM) that keep applications available during planned or unplanned maintenance.


Refer to the idea of increasing or decreasing resources and services based on demand and workload. Vertical scaling aka. Scale-up Add more resources to exciting service and Horizontal Scaling aka Scale Down means Add more to the server.


Refer to how the cloud admin can add or remove resources based on the demand.

Cloud Agility

Refer to how cloud admin can rapidly change and IT Infrastructure to adapt to evolving to the business. For example, in case of business goes down so the Cloud admin can reduce the resources for the organization so the cost would be minimal.

Fault Tolerance

Refer to Redundancy built-in cloud service as one service or component failed so the backup component makes it a palace.

Disaster Recovery

Refer to the ability to recover from the rare but major incident, a wide-scale failure that affects an entire region. Disaster recovery includes data backup and archiving backup and also restoring from a database backup.

Describe the Principles of Economies of Scale

Economies of Scale is the ability to do things more efficiently or at a low cost per unit when operating g at a larger scale. This cost Advantage is an important benefit in cloud computing.

Cloud providers such as Microsoft, Google, and Amazon are large businesses leveraging the benefits of economies of scale. These providers can then pass the savings on to their customers.

Economies of Scale Whitepapers

Describe the differences between:

  • Capital Expenditure (CapEx)
  • Operational Expenditure (OpEx)

Capital Expenditure (CapEx)

CapEx is the spending of money on physical infrastructure upfront and then deducting that expense from your tax bill over time. CapEx is an upfront cost, which has a value that reduces over time.

Operational Expenditure (OpEx)

OpEx is spending money on services or products now and being billed for them now. You can deduct this expense from your tax bill in the same year. There’s no upfront cost. You pay for a service or product as you use it.

Describe the consumption-based model

Capital Expenditure (CapEx) Cost

  • Server Costs
  • Storage Cost
  • Data Center Infrastructure Cost
  • Network Cost
  • Organization Continuity and Disaster
  • Recovery Cost
  • Backup and Archive Cost
  • Technical Personnel

Operational Expenditure (OpEx) Cost

  • Leasing Software and Customization feature cost
  • Scale charge based on usage/demand for fixing hardware and Capacity
  • Billing at the user or the Organization

Comparing Benefits Between Capital Expenditure vs Operational Expenditure

Capital Expenditure

With capital expenditures, you plan your expenses at the start of a project or budget period. Your costs are fixed, meaning you know exactly how much is being spent. This is appealing when you need to predict the expenses before a project starts due to a limited budget.

Operational Expenditure

OpEx is particularly appealing if the demand fluctuates or is unknown. Cloud services are often said to be agile. Cloud agility is the ability to rapidly change an IT infrastructure to adapt to the evolving needs of the business. For example, if your service peaks one month, you can scale to demand and pay a larger bill for the month. If the following month the demand drops, you can reduce the used resources and be charged less. This agility lets you manage your costs dynamically, optimizing spending as requirements change.

Describe the differences between Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS), and Software-as-a-Service (SaaS)

Infrastructure-as-a-Service (IaaS)

Infrastructure as a Service is the most flexible category of cloud services. It aims to give you complete control over the hardware that runs your application (IT infrastructure servers and virtual machines (VMs), storage, networks, and operating systems). Instead of buying hardware, with IaaS, you rent it. It’s an instant computing infrastructure, provisioned, and managed over the internet.

Platform-as-a-Service (PaaS)

PaaS provides an environment for building, testing, and deploying software applications. The goal of PaaS is to help you create an application quickly without managing the underlying infrastructure. For example, when deploying a web application using PaaS, you don’t have to install an operating system, web server, or even system updates.

Software-as-a-Service (SaaS)

SaaS is software that is centrally hosted and managed for the end customer. It is usually based on an architecture where one version of the application is used for all customers, and licensed through a monthly or annual subscription. Microsoft 365, Skype, Gmail, and Dynamics CRM Online are perfect examples of SaaS software.

Cost and Ownership

Comparing IaaS, PaaS and SaaS

As you’ve learned, IaaS provides you with the greatest flexibility. You can install your own software and your own components, and you control when the software and operating system are updated. An additional benefit is that you pay for your resources only when they’re being used, so IaaS has the ability to reduce your operational expenses. Even though you can save costs by turning off VMs you aren’t using, the higher costs associated with installing and maintaining your VMs might offset that benefit. PaaS services offer you some of the same flexibility as IaaS services without the need to manage the infrastructure. In a PaaS service, you are responsible only for the application that’s installed in the cloud. This can be your own application or an application developed by someone else (for example, a WordPress system or an e-commerce solution), but in either case, you are responsible for the application. PaaS services are popular for developer teams who are looking to move on-premises applications to the cloud easily and quickly, and they typically offer many different deployment options to make that as easy as possible. PaaS services also offer more features than IaaS services, because the cloud provider installs their own software and features on the platform. Any application running in a PaaS service, however, can be impacted by updates and version changes in the underlying software, and that can mean increased costs associated with testing an application before the cloud provider rolls out changes. SaaS services are quite a bit different than IaaS or PaaS services because they are completely managed and maintained by the cloud provider. You don’t have the option of installing any of your own software with a SaaS service, so the deciding factor is related entirely to whether or not the provided-software meets your needs. The benefit of a SaaS service is that it largely removes the IT burden from your company, and it enables everyone in your company to access the software on multiple devices from just about anywhere Internet access is available. You also benefit from data backup that the cloud provider includes in their infrastructure. If you need to customize the application or have any control over its configuration, however, SaaS may not be a good choice for you.

Management Resposibilities

Describe the differences between Public, Private, and Hybrid cloud models

Public Cloud

This is the most common deployment model. In this case, you have no local hardware to manage or keep up-to-date — everything runs on your cloud provider’s hardware. In some cases, you can save additional costs by sharing computing resources with other cloud users.


  • High scalability/agility — you don’t have to buy a new server to scale
  • Pay-as-you-go pricing — you pay only for what you use, no CapEx costs
  • You’re not responsible for maintenance or updates of the hardware


  • There may be specific security requirements that cannot be met by using public cloud
  • There may be government policies, industry standards, or legal requirements that public clouds cannot meet
  • You don’t own the hardware or services and cannot manage them as you may want to
  • Unique business requirements, such as having to maintain a legacy application might be hard to meet

Private Cloud

In a private cloud, you create a cloud environment in your own datacenter and provide self-service access to compute resources to users in your organization. This offers a simulation of a public cloud to your users, but you remain completely responsible for the purchase and maintenance of the hardware and software services you provide.


  • You can ensure the configuration can support any scenario or legacy application
  • You have control (and responsibility) over security
  • Private clouds can meet strict security, compliance, or legal requirements


  • You have some initial CapEx costs and must purchase the hardware for startup and maintenance
  • Owning the equipment limits the agility — to scale you must buy, install, and set up new hardware
  • Private clouds require IT skills and expertise that’s hard to come by

Hybrid Cloud

A hybrid cloud combines public and private clouds, allowing you to run your applications in the most appropriate location. For example, you could host a website in the public cloud and link it to a highly secure database hosted in your private cloud (or on-premises datacenter).


  • You can keep any systems running and accessible that use out-of-date hardware or an out-of-date operating system
  • You have flexibility with what you run locally versus in the cloud
  • You can take advantage of economies of scale from public cloud providers for services and resources where it’s cheaper, and then supplement with your own equipment when it’s not
  • You can use your own equipment to meet security, compliance, or legacy scenarios where you need to completely control the environment


  • It can be more expensive than selecting one deployment model since it involves some CapEx cost upfront
  • It can be more complicated to set up and manage

Check your Knowledge


  • Cloud providers offer service-level agreements (SLAs) that guarantee a certain level of availability, but only for those systems that are controlled by them.
  • Moving to the cloud can help avoid downtime caused by network outages, system outages, and power outages. It can also help you if you need to diagnose problems with an application or problems with an external system that your application uses.
  • You can scale up (or vertically) when you want to add additional CPUs or more memory using a more powerful VM.
  • You can scale out (or horizontally) if you want to add more VMs to handle the additional load.
  • Cloud providers give you ways to automatically scale based on usage patterns, resource utilization, and times of the day. This is referred to as elasticity.
  • Cloud providers monitor the health of the infrastructure. When a VM becomes unhealthy, the cloud provider can automatically move you to a healthy VM without you having to do anything. This is called fault tolerance.
  • Cloud providers also operate across multiple data centers that are in different regions of the world. If a natural disaster (or any other disaster) happens in one region, you can switch over to another region, assuming you have replicated your environment in multiple regions. This kind of planning is called Business Continuity and Disaster Recovery Planning, and cloud providers often have features in place to make implementing a plan easy. This is often referred to as disaster recovery.
  • Because you are using infrastructure owned by the cloud provider, moving to the cloud reduces your capital expenses, the major expenses that are incurred for infrastructure and other major purchases. Cloud providers take advantage of the principle of economies of scale by purchasing large amounts of infrastructure to be used by cloud consumers.
  • Day-to-day expenses (operational expenses) can also be reduced in the cloud because you pay only for those resources you are using at any particular time. This consumption-based model is a key benefit of the cloud.
  • Infrastructure-as-a-Service (IaaS) offers infrastructure running in the cloud, but you have to maintain the operating system and what’s installed on that infrastructure. IaaS services offer you the most control in the cloud, but they also carry the largest management burden.
  • Platform-as-a-Service (PaaS) offloads the management of the infrastructure, and it also offloads the operating system and components installed on the VMs to the cloud provider. You are responsible for your application. PaaS services also offer many additional features that make it easy to add functionality to an application without having to write complex code. Development teams also have a wide variety of deployment methods available, and the cloud provider often automates much of that process.
  • Software-as-a-Service (SaaS) provides a hosted application in the cloud that is most commonly accessed using a web browser. In a SaaS service, the cloud provider manages everything for you. You are essentially renting the use of the software from the cloud provider. A big benefit of SaaS is that it makes applications easily-accessible by employees in the field on any device.
  • The public cloud model is sometimes referred to as a multitenant environment. Multiple companies and users share the same infrastructure. VMs and other infrastructure are allocated to users as they need them, and when they no longer need them, they are returned to the pool to be used by other users. The network is available publicly over the Internet, but you do have the ability to put security methods in place to control access to your resources.
  • The private cloud model is sometimes referred to as a single-tenant environment. All infrastructure is private to an individual or a company, and the network is only available within the private cloud itself. It is not exposed to the Internet. In many cases, the infrastructure used in a private cloud is owned by the company, but not always. It’s possible to host a private cloud in a third-party data center.
  • A hybrid cloud model is a mixture of public and private cloud models. Hybrid clouds are often used when a company needs to use on-premises resources in a cloud application.

More Resources

  1. Cloud Concepts — Principle of Cloud Computing

Module -2

Describe Core Azure Services