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Understanding public cloud deployment model, its architecture, benefits, limitations, and major providers like AWS, Azure, and GCP.
A public cloud is a cloud computing environment owned and operated by a third-party service provider and delivered over the public internet. Resources such as servers, storage, and networking are shared among multiple organizations (tenants) while maintaining logical isolation.
Public Cloud Architecture
┌─────────────────────────────────────────────────────────────┐
│ PUBLIC CLOUD PROVIDER │
│ │
│ ┌─────────────────────────────────────────────────────┐ │
│ │ Region: US-East-1 │ │
│ │ ┌───────────────┐ ┌───────────────┐ ┌─────────┐ │ │
│ │ │ AZ-1a │ │ AZ-1b │ │ AZ-1c │ │ │
│ │ │ ┌───┐ ┌───┐ │ │ ┌───┐ ┌───┐ │ │ ┌───┐ │ │ │
│ │ │ │T-A│ │T-B│ │ │ │T-C│ │T-A│ │ │ │T-B│ │ │ │
│ │ │ └───┘ └───┘ │ │ └───┘ └───┘ │ │ └───┘ │ │ │
│ │ └───────────────┘ └───────────────┘ └─────────┘ │ │
│ └─────────────────────────────────────────────────────┘ │
│ │
│ T-A = Tenant A T-B = Tenant B T-C = Tenant C │
│ (Shared infrastructure, logical isolation) │
└─────────────────────────────────────────────────────────────┘
│ │ │
┌────┴────┐ ┌───┴────┐ ┌───┴────┐
│Company A│ │Company B│ │Company C│
└─────────┘ └────────┘ └────────┘
Key Characteristics
| Feature | Description |
|---|---|
| Ownership | Cloud provider owns and manages all hardware |
| Access | Available to anyone via the internet |
| Multi-tenancy | Multiple organizations share infrastructure |
| Pricing | Pay-as-you-go or subscription model |
| Maintenance | Provider handles all updates and maintenance |
| Scalability | Virtually unlimited resources available |
Major Public Cloud Providers
AWS (Amazon Web Services)
- Market Share: ~32% (2024)
- Regions: 33+ globally
- Key Services: EC2, S3, Lambda, RDS
Example
# Launch a web server on AWS public cloud
aws ec2 run-instances \
--image-id ami-0c55b159cbfafe1f0 \
--instance-type t3.micro \
--security-group-ids sg-0123456789abcdef0 \
--key-name my-key \
--tag-specifications 'ResourceType=instance,Tags=[{Key=Name,Value=PublicWebServer}]'
Microsoft Azure
- Market Share: ~23% (2024)
- Regions: 60+ globally
- Key Services: Virtual Machines, Blob Storage, Azure Functions
bash example
# Create a VM on Azure public cloud
az vm create \
--resource-group myResourceGroup \
--name myPublicVM \
--image Ubuntu2204 \
--size Standard_B2s \
--admin-username azureuser \
--generate-ssh-keysGoogle Cloud Platform (GCP)
- Market Share: ~11% (2024)
- Regions: 40+ globally
- Key Services: Compute Engine, Cloud Storage, BigQuery
bash example
# Create an instance on GCP
gcloud compute instances create public-web-server \
--zone=us-central1-a \
--machine-type=e2-medium \
--image-family=ubuntu-2204-lts \
--image-project=ubuntu-os-cloudAdvantages of Public Cloud
- No Capital Expenditure: Zero upfront hardware investment
- Global Scale: Deploy in 100+ locations worldwide instantly
- Elastic Scaling: Scale from 1 to 10,000 servers automatically
- Managed Services: Databases, AI/ML, analytics without server management
- Innovation Speed: Access new technologies immediately
- High Availability: Built-in redundancy and disaster recovery
Limitations of Public Cloud
- Security Concerns: Data resides on shared infrastructure
- Compliance Challenges: Some regulations restrict public cloud use
- Vendor Lock-In: Proprietary services make migration difficult
- Variable Costs: Usage spikes can cause unexpected bills
- Limited Customization: Cannot modify underlying hardware
Who Should Use Public Cloud?
- Startups needing rapid scaling without capital investment
- Companies with variable workloads (seasonal traffic)
- Organizations wanting managed services (databases, AI/ML)
- Development and testing environments
- Web applications serving global audiences
Public Cloud Security Model
Example
{
"provider_responsibility": [
"Physical data center security",
"Hardware maintenance",
"Network infrastructure",
"Hypervisor security",
"Global network backbone"
],
"customer_responsibility": [
"Data encryption",
"Access management (IAM)",
"Application security",
"Network configurations (Security Groups)",
"Operating system patches (for IaaS)"
]
}
Interview Questions
- What is a public cloud and how does it differ from private cloud?
A public cloud is owned by a third-party provider and shared among multiple organizations via the internet. Unlike private cloud, resources are multi-tenant, costs are shared, and there's no hardware ownership.
- Name the top three public cloud providers and their market positions.
AWS (~32% share, pioneer since 2006), Microsoft Azure (~23%, enterprise integration), and Google Cloud Platform (~11%, strong in data analytics and AI/ML).
- What security concerns exist with public cloud?
Data is stored on shared infrastructure, raising concerns about data isolation, compliance with regulations, insider threats at the provider level, and dependency on the provider's security practices.
- When would you NOT recommend public cloud?
When strict data sovereignty laws prohibit data leaving specific jurisdictions, when ultra-low latency is critical, when regulatory compliance forbids shared infrastructure, or when workloads are highly predictable (making reserved capacity cheaper on-premises).
- How does multi-tenancy work in public cloud while maintaining security?
Through logical isolation using hypervisors (separating VMs), virtual networks (VPCs), IAM policies, and encryption. Each tenant's data and compute resources are isolated despite sharing physical hardware.
Exam Focus
Revise definitions, diagrams, examples, and short-answer points for Public Cloud.
Interview Use
Prepare one clear explanation, one practical example, and one common mistake for this Cloud Computing topic.
Search Terms
cloud-computing, cloud computing, cloud, computing, deployment, models, public, public cloud
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