Introduction to Cloud Computing

Learning objectives#

• Explain what cloud computing is
• Compare IaaS, PaaS and SaaS
• Describe elasticity and pay-as-you-go pricing
• Understand the shared responsibility model

Explanation#

Before the cloud, companies bought servers, waited weeks for delivery and paid for capacity even when it sat idle. In the cloud you create resources in minutes and pay only while you use them.

IaaS (Infrastructure as a Service) gives you virtual machines and networks — you manage the operating system. PaaS (Platform as a Service) runs your code for you — you manage only the app. SaaS (Software as a Service) is a finished product such as Microsoft 365 or Gmail.

Elasticity means scaling up for a festival sale and back down afterwards, automatically. Spending moves from up-front capital expense (CapEx) to monthly operating expense (OpEx).

Security is shared: the provider secures the data centres and physical hardware; you secure your data, identities, configuration and code. The more managed the service, the less you have to look after.

Code example: Who manages what?#

1                    On-premises   IaaS (VM)    PaaS (App Service)   SaaS (Microsoft 365)
2Data & access          You           You           You                  You
3Application code       You           You           You                  Provider
4Runtime (.NET/Node)    You           You           Provider             Provider
5Operating system       You           You           Provider             Provider
6Servers & network      You           Provider      Provider             Provider
7Data centre            You           Provider      Provider             Provider

Moving right, you manage less and the provider manages more — but you are always responsible for your data and who can access it.

This example is illustrative. Copy or download it and run it in your own environment; the expected output is shown above.

Step-by-step explanation#

1. On-premises, you own every layer.
2. With IaaS the provider runs the hardware; you still patch the OS.
3. With PaaS you just deploy code; the platform handles the OS and runtime.
4. With SaaS you only manage users and data.

Real-world use case#

Common mistakes#

Best practices#

• Prefer managed (PaaS/serverless) services when they fit
• Set budgets and alerts from day one
• Automate infrastructure with code
• Learn the shared responsibility model for each service you use

Remember this#

Practice exercise#

1Azure Virtual Machines → IaaS
2Azure App Service → PaaS
3Outlook.com → SaaS
4Azure SQL Database → PaaS (a managed database)

Mini quiz#

Want more? Practise all Microsoft Azure MCQs · Microsoft Azure interview questions

Related topics#

My notes#

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