What Is Cloud Computing?

Quick Answer: Cloud computing is the on-demand delivery of compute power, database storage, applications, and other IT resources through a cloud services platform via the internet with pay-as-you-go pricing. Instead of buying, owning, and maintaining physical data centers and servers, you access technology services on an as-needed basis from a cloud provider like AWS.

The NIST Definition

The National Institute of Standards and Technology (NIST) defines cloud computing through five essential characteristics:

Traditional IT vs. Cloud Computing

Understanding the shift from traditional IT to cloud is essential for the exam:

Traditional (On-Premises) IT

• Buy hardware upfront (servers, storage, networking)
• Build and staff your own data center
• Estimate capacity months or years in advance
• Maintain everything: hardware, cooling, power, security
• Capital expenditure (CapEx): Large upfront investment
• Long provisioning times: Weeks or months to set up new servers

Cloud Computing (AWS)

• Rent resources on demand — no upfront hardware purchases
• AWS manages the data centers, hardware, and infrastructure
• Scale dynamically — add or remove resources in minutes
• Pay only for what you use (metered billing)
• Operating expenditure (OpEx): Variable cost based on consumption
• Fast provisioning: Launch new servers in seconds

On the Exam: Expect questions comparing traditional IT with cloud computing. The key advantages are: trade CapEx for OpEx, stop guessing capacity, increase speed and agility, stop spending money running data centers, and go global in minutes.

The Six Advantages of Cloud Computing

AWS articulates six advantages of cloud computing that are frequently tested:

1. Trade Fixed Expense for Variable Expense

Instead of investing heavily in data centers and servers before you know how you will use them, you pay only when you consume computing resources and pay only for how much you consume.

2. Benefit from Massive Economies of Scale

Because usage from hundreds of thousands of customers is aggregated in the cloud, providers like AWS can achieve higher economies of scale, which translates into lower pay-as-you-go prices.

3. Stop Guessing Capacity

Eliminate guessing on infrastructure capacity needs. With cloud computing, you can access as much or as little capacity as you need, and scale up and down as required with only a few minutes' notice.

4. Increase Speed and Agility

New IT resources are only a click away, which means you reduce the time to make those resources available to your developers from weeks to just minutes. This results in a dramatic increase in agility for the organization.

5. Stop Spending Money Running and Maintaining Data Centers

Focus on projects that differentiate your business, not the heavy lifting of racking, stacking, and powering servers. Let AWS handle the undifferentiated infrastructure work.

6. Go Global in Minutes

Deploy your application in multiple Regions around the world with just a few clicks. This means you can provide lower latency and a better experience for your customers at minimal cost.

AWS Global Infrastructure

AWS operates one of the largest and most reliable cloud infrastructures in the world:

Regions

A Region is a separate geographic area (e.g., us-east-1 in Northern Virginia, eu-west-1 in Ireland). Each Region is completely independent, meaning data does not leave a Region unless you explicitly move it. This is critical for data sovereignty and compliance.

How to choose a Region:

• Compliance: Some data must remain in specific countries
• Latency: Choose the Region closest to your users
• Service availability: Not all services are available in every Region
• Pricing: Costs vary by Region

Availability Zones

Each Region contains two or more Availability Zones (AZs). Each AZ consists of one or more discrete data centers with redundant power, networking, and connectivity. AZs within a Region are connected through low-latency links but are physically separated to protect against local failures (floods, fires, earthquakes).

Edge Locations

Edge locations are data centers used by Amazon CloudFront (CDN) and other services to cache content closer to end users for lower latency. There are far more edge locations than Regions or AZs.