Module 1: Cloud and AWS Foundations

Cloud Concepts and Benefits

Before you can choose the right AWS service or answer an exam question about cost, you need a clear picture of what cloud computing actually is and why organisations move to it. The AWS Certified Cloud Practitioner exam opens with this domain, and almost every later topic, from pricing to security, builds on these ideas. If you understand the "why", the "what" becomes much easier to remember.

What cloud computing means

AWS defines cloud computing as the on-demand delivery of IT resources over the internet with pay-as-you-go pricing. Instead of buying servers, storage and networking equipment and running them in your own building, you rent those resources from a provider and pay only for what you use. You request a server through a web console or an API call, it is ready in minutes, and you can switch it off when you no longer need it.

Compare this with the traditional, or on-premises, model. A Nairobi logistics company that wants a new customer portal on-premises must estimate how much capacity it will need for the next three to five years, buy hardware, wait for delivery, rack it, install operating systems, and pay for power, cooling and security for the server room. If the estimate is too low, the portal slows down when customers arrive. If it is too high, money sits idle in unused machines.

The service models and deployment models

The exam expects you to recognise three service models:

• Infrastructure as a Service (IaaS): you rent basic building blocks such as virtual machines, storage and networks, and you manage the operating system and everything above it. Amazon EC2 is the classic example.
• Platform as a Service (PaaS): the provider manages the underlying infrastructure and operating system, and you focus on deploying your application. AWS Elastic Beanstalk is an example.
• Software as a Service (SaaS): you use a complete application run by the provider, such as web-based email or accounting software.

You should also know the deployment models:

• Cloud (all-in): applications run fully in the cloud.
• On-premises (sometimes called private cloud): resources run in your own data centre, often using virtualisation tools.
• Hybrid: cloud resources are connected to on-premises systems, for example a bank that keeps a core system in its own data centre but runs its mobile app back end on AWS.

The six advantages of cloud computing

AWS describes six advantages, and exam questions often describe a business situation and ask which advantage it shows. Learn them as a set:

1. Trade fixed expense for variable expense. Instead of large upfront spending on data centres and servers (capital expense), you pay only when you consume resources (operating expense).
2. Benefit from massive economies of scale. Because a provider serves a very large number of customers, it can achieve lower costs per unit and pass savings on as lower prices.
3. Stop guessing capacity. You scale up or down as demand changes rather than buying for a forecast that may be wrong.
4. Increase speed and agility. New resources are available in minutes, so teams can experiment and deliver faster.
5. Stop spending money running and maintaining data centres. Your staff focus on your customers and products rather than on racking servers.
6. Go global in minutes. You can deploy applications in AWS Regions around the world to serve users with lower latency.

Worked example: matching scenarios to advantages

Imagine an online ticket seller in Nairobi. Most weeks it serves a few thousand visitors, but when a major concert goes on sale, traffic multiplies for two days.

Notice the wording. "Automatically adds capacity when needed" points to elasticity and stop guessing capacity. "Lower prices because AWS is very large" points to economies of scale. Train yourself to spot these keywords.

Related terms you will see

Elasticity is the ability to add and remove resources automatically as demand changes. Scalability is the ability to grow to handle more load. High availability means a system keeps running even when some components fail, usually by running in more than one location. Agility refers to how quickly you can try new ideas.

Common mistakes to avoid

• Assuming the cloud is always cheaper. It removes upfront costs, but badly managed resources left running can cost more than expected. Cost management is a skill you will learn later in this course.
• Confusing elasticity with economies of scale. Elasticity is about your usage changing; economies of scale are about AWS's size lowering prices.
• Thinking "cloud" means you have no responsibilities. You still manage your data, access and configuration, as the shared responsibility model will show.