Key Terms: Scalability, Elasticity, and On-Demand Resources

Lesson Objectives

By the end of this lesson, you will:

1. Understand what scalability, elasticity, and on-demand resources mean in cloud computing.
2. Explore how these concepts solve real-world challenges through relatable scenarios.
3. Learn how AWS makes these capabilities accessible.

Introduction: A Bakery’s Big Break

Imagine you own a small bakery. You sell delicious cookies, and most of your customers come from the neighborhood. You bake a steady number of cookies each day, using a small oven that meets your needs. One day, a food blogger writes a glowing review, and suddenly, people from all over the city want your cookies.

Your small oven can’t handle the sudden demand, and you’re forced to turn customers away. What if you had an oven that could grow or shrink based on how many cookies you needed to bake? That’s what scalability, elasticity, and on-demand resources are like in the world of cloud computing. They let businesses handle unexpected demand without missing opportunities—or wasting resources.

What is Scalability?

Scalability is the ability to handle an increase in workload by adding more resources. It’s like getting extra ovens or upgrading to a bigger one when you have more orders.

Scenario: Scaling Up Your Bakery

At first, your small oven can bake 100 cookies per hour. When demand spikes to 1,000 cookies per hour, you need more capacity. You have two options:

1. Vertical Scaling: Replace your small oven with a bigger one that can bake 1,000 cookies at once.
   • In cloud terms, this is like upgrading your server to handle more traffic.
   • AWS Example: Switching an EC2 instance from t2.micro to m5.large.
2. Horizontal Scaling: Buy 10 additional ovens, each baking 100 cookies.
   • In cloud terms, this means adding more servers to share the workload.
   • AWS Example: Using an Auto Scaling group to add more EC2 instances as traffic grows.

What is Elasticity?

Elasticity is the ability to scale resources automatically based on demand. It’s like having ovens that appear during peak hours and disappear when the rush is over, so you’re not paying for unused capacity.

Scenario: Handling Morning and Evening Rush

Your bakery is busiest during breakfast and dinner times, but quiet in the afternoon. Instead of keeping all ovens running all day, elasticity ensures you only use ovens when you need them.

• During a Rush: Extra ovens turn on to handle the demand.
• During Slow Times: Unneeded ovens turn off to save energy and costs.

AWS Example:
AWS Auto Scaling launches more EC2 instances when traffic increases and terminates them when demand decreases, ensuring you only pay for what you use.

What are On-Demand Resources?

On-demand resources let you pay only for what you need, when you need it. It’s like renting ovens for a few hours instead of buying them outright.

Scenario: Launching Your Bakery in a New City

You’re testing your bakery in a new location. Instead of buying equipment, you rent ovens to see how the market responds. If it works, you can scale up. If it doesn’t, you can stop renting without losing money.

AWS Example:

• Amazon EC2 On-Demand Instances: Rent virtual servers by the hour or second, with no upfront costs.
• Amazon S3: Store only the files you need, paying per GB of data.

How AWS Brings These Concepts to Life

Let’s see how AWS combines these concepts to solve real-world problems:

1. Scalability: Auto Scaling groups ensure your website or application grows to meet demand.
2. Elasticity: Elastic Load Balancers distribute traffic across available resources and adjust as needed.
3. On-Demand Resources: Services like EC2 and S3 let you provision resources instantly, without long-term commitments.

Reflection: What Would You Do?

Think about how businesses like Amazon or Spotify handle millions of users. They don’t buy fixed infrastructure for peak traffic—they rely on scalability, elasticity, and on-demand resources to adjust in real time. Now, imagine applying these principles to your own projects.

What would you build if you knew you could scale infinitely, pay only for what you use, and adapt instantly to changing needs?