Explore the basics of cloud computing, including its definition, key characteristics, advantages, and different service models (IaaS, PaaS, SaaS).
Introduction to Cloud Computing
Quick reference guide – concise, organized, and easy to read.
1. What Is Cloud Computing?
| Definition |
Key Idea |
| Delivery of computing resources (servers, storage, databases, networking, software, analytics, AI) over the Internet (“the cloud”) on a pay‑as‑you-go basis. |
Users access services on demand without owning or managing the underlying hardware. |
2. Core Characteristics (NIST Model)
| Characteristic |
What It Means |
Example |
| On‑Demand Self‑Service |
Users can provision resources automatically, without human interaction. |
Spin up a virtual machine via a web portal. |
| Broad Network Access |
Services are reachable over standard networks (Internet, mobile, LAN). |
Access a cloud‑hosted database from a laptop or smartphone. |
| Resource Pooling |
Multi‑tenant model; physical resources are shared and dynamically allocated. |
Multiple customers run workloads on the same physical server cluster. |
| Rapid Elasticity |
Resources scale out/in quickly to match workload fluctuations. |
Auto‑scale a web‑app from 2 to 200 instances during a sale. |
| Measured Service |
Usage is monitored, controlled, and billed automatically. |
Billing per GB of storage used per month. |
3. Service Models
| Model |
Description |
Typical Offerings |
Who Uses It? |
| IaaS (Infrastructure as a Service) |
Raw compute, storage, networking. |
VMs, block storage, load balancers, virtual networks. |
Sysadmins, developers needing full control of OS & runtime. |
| PaaS (Platform as a Service) |
Managed runtime environment & development tools. |
Managed databases, app hosting, serverless functions, CI/CD pipelines. |
Developers focusing on code, not infrastructure. |
| SaaS (Software as a Service) |
Fully functional applications delivered over the web. |
Email (e.g., Gmail), CRM (Salesforce), collaboration (Office 365). |
End‑users who need ready‑to‑use software. |
| FaaS (Function as a Service) – a subset of serverless |
Executes single functions in response to events. |
AWS Lambda, Azure Functions, Google Cloud Functions. |
Event‑driven workloads, micro‑services, rapid prototyping. |
4. Deployment Models
| Model |
Ownership |
Accessibility |
Typical Use Cases |
| Public Cloud |
Provider owns & operates the infrastructure. |
Open to anyone (pay‑per‑use). |
Start‑ups, variable workloads, cost‑sensitive projects. |
| Private Cloud |
Single organization owns or leases dedicated resources. |
Restricted to the organization. |
Regulated industries, legacy migration, strict security/compliance. |
| Hybrid Cloud |
Combination of public & private, linked for data & app portability. |
Both internal and external users. |
Burst to public cloud during peaks, keep sensitive data on‑prem. |
| Community Cloud |
Shared by several organizations with common concerns (e.g., government). |
Access limited to the community members. |
Joint research projects, industry consortia. |
5. Major Cloud Providers (2024)
| Provider |
Core Strengths |
Notable Services |
| Amazon Web Services (AWS) |
Largest ecosystem, breadth of services. |
EC2, S3, RDS, Lambda, SageMaker. |
| Microsoft Azure |
Strong integration |
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