What is Cloud Computing? A Simple Explanation for 2026

Cloud Computing — At a Glance:

Simple definition:
  Renting computing power over the internet
  instead of buying and running your own servers.

Five key characteristics (NIST):
  1. On-demand self-service
  2. Broad network access
  3. Resource pooling
  4. Rapid elasticity
  5. Measured / pay-per-use service

Common service categories:
  - Compute (virtual machines, containers, serverless)
  - Storage (object, block, file)
  - Databases (managed SQL and NoSQL)
  - Networking (VPC, load balancers, DNS)
  - AI/ML (managed training and inference)

Major providers (2026):
  - AWS
  - Microsoft Azure
  - Google Cloud
  - Oracle Cloud, IBM Cloud, regional players

What cloud is NOT:
  - Not a single product
  - Not "someone else's computer" only
  - Not automatically cheaper — it depends on usage

Week 1 Review:
□ Can I define cloud computing in one sentence?
□ Do I understand cloud vs on-premises?
□ Do I know what virtualisation is?

Week 2 Review:
□ Do I know the five NIST characteristics?
□ Can I explain elasticity with an example?
□ Do I understand pay-per-use billing?

Week 3 Review:
□ Can I name five common cloud use cases?
□ Can I match each use case to a service type?
□ Do I know what managed services are?

Week 4 Review:
□ Can I explain when on-premises makes sense?
□ Do I understand the cost trade-offs?
□ Can I describe the control trade-off?

Cloud Service Models — Daily Study Schedule:
7:00 AM — Wake up, quick revision (20 min)
8:00 AM — Review the day's concepts
9:00 AM — Deep study (2 hours)
   - Week 5: IaaS — VMs, networking, storage
   - Week 6: PaaS — runtimes, managed services
   - Week 7: SaaS — apps, data, configuration
   - Week 8: Choosing the right model
12:00 PM — Lunch break
1:00 PM — Hands-on practice (2 hours)
   - Launch a VM / deploy an app / configure a SaaS tool
3:00 PM — Review notes, plan tomorrow
5:00 PM — Exercise, rest
8:00 PM — Read docs / watch demos (30 min)
10:00 PM — Wind down

Week 5 Review:
□ Can I launch and connect to a VM?
□ Do I understand VPC / networking basics?
□ Do I know what I manage vs what the provider manages?

Week 6 Review:
□ Can I deploy an app without touching a server?
□ Do I understand managed databases?
□ Can I explain PaaS in one sentence?

Week 7 Review:
□ Can I give three real examples of SaaS?
□ Do I understand why SaaS is the most abstract model?
□ Can I explain the control vs convenience trade-off?

Week 8 Review:
□ Can I match a workload to the right service model?
□ Do I understand the cost implications of each model?
□ Can I justify a choice in an interview answer?

Service Model — Who Manages What?

On-Premises:
  You:      everything (hardware, OS, runtime, app, data)

IaaS (e.g. EC2, Compute Engine, Azure VMs):
  Provider: hardware, networking, storage
  You:      OS, runtime, app, data

PaaS (e.g. App Service, Elastic Beanstalk, Cloud Run):
  Provider: hardware, networking, storage, OS, runtime
  You:      app, data

SaaS (e.g. Gmail, Microsoft 365, Salesforce):
  Provider: everything
  You:      your data and configuration

Service Model — Real Examples:

IaaS:
  - AWS EC2
  - Google Compute Engine
  - Azure Virtual Machines
  - DigitalOcean Droplets

PaaS:
  - AWS Elastic Beanstalk
  - Azure App Service
  - Google Cloud Run
  - Heroku
  - Render

SaaS:
  - Gmail / Google Workspace
  - Microsoft 365
  - Salesforce
  - Slack
  - Notion
  - Zendesk

Rule of thumb:
  Need full control of the OS?        → IaaS
  Want to just push code?             → PaaS
  Want a tool that already works?     → SaaS

Deployment Models — Daily Study Schedule:
7:00 AM — Wake up, quick revision (20 min)
8:00 AM — Review the day's concepts
9:00 AM — Deep study (2 hours)
   - Week 9: Public cloud
   - Week 10: Private cloud
   - Week 11: Hybrid & multi-cloud
   - Week 12: Provider comparison
12:00 PM — Lunch break
1:00 PM — Hands-on practice (2 hours)
   - Explore one provider console
   - Compare pricing pages
   - Read architecture case studies
3:00 PM — Review notes, plan tomorrow
5:00 PM — Exercise, rest
8:00 PM — Read provider docs / blogs (30 min)
10:00 PM — Wind down

Week 9 Review:
□ Do I understand public cloud?
□ Can I name three benefits?
□ Do I know the main drawbacks (cost control, lock-in)?

Week 10 Review:
□ Do I understand private cloud?
□ Which industries prefer it and why?
□ Do I understand compliance requirements?

Week 11 Review:
□ Can I explain hybrid cloud with an example?
□ Do I understand multi-cloud?
□ Can I list the trade-offs?

Week 12 Review:
□ Have I picked one primary cloud?
□ Do I know the main services of that cloud?
□ Have I checked job demand for that cloud?

Cloud Providers — 2026 Snapshot:

AWS:
  Strengths: breadth of services, largest job market
  Good first pick if: you want maximum hiring demand

Microsoft Azure:
  Strengths: enterprise, Microsoft ecosystem, hybrid
  Good first pick if: you target enterprises or .NET shops

Google Cloud:
  Strengths: data, ML, Kubernetes (GKE)
  Good first pick if: you target data / AI-heavy roles

Tip:
  Learn one deeply, then map the concepts to the others.
  The mental model transfers; the service names do not.

Deployment Models — Quick Comparison:

Public cloud:
  - Shared infrastructure
  - Fast to start, elastic, pay-per-use
  - Less control over underlying hardware

Private cloud:
  - Dedicated to one organisation
  - More control, easier compliance
  - Higher cost and maintenance

Hybrid cloud:
  - Mix of public + private
  - Run sensitive workloads privately, burst to public
  - Most common in large enterprises

Multi-cloud:
  - Using two or more public providers
  - Avoids single-vendor lock-in
  - Adds operational complexity

Community cloud:
  - Shared by several organisations with common needs
  - Common in government, healthcare, education

Cloud Cost Checklist:

Before launch:
☐ Set a billing budget and alert
☐ Tag every resource (env, owner, project)
☐ Choose the right region (latency + price)
☐ Pick the smallest instance that works

During operation:
☐ Rightsize instances monthly
☐ Delete unused volumes and snapshots
☐ Use object storage lifecycle rules
☐ Turn off non-prod environments at night
☐ Use reserved / savings plans for steady workloads

After each month:
☐ Review top 5 cost drivers
☐ Compare cost vs usage growth
☐ Document one optimisation to apply

# List S3 buckets
aws s3 ls

# Copy a file to S3
aws s3 cp index.html s3://my-bucket/

# List running EC2 instances
aws ec2 describe-instances \
  --query "Reservations[].Instances[].{Id:InstanceId,State:State.Name}"

# List IAM users
aws iam list-users

# Check current account identity
aws sts get-caller-identity

Architecture Notes:

Workload:      _______________
Users:         _______________
SLA:           _______________

Compute:       _______________
Storage:       _______________
Database:      _______________

Network:       _______________
Security:      _______________
Cost estimate: _______________

Why this design:
1.
2.
3.

Trade-offs accepted:
1.
2.