Public Cloud
What Is the Public Cloud?
The public cloud is a model of cloud computing in which computing resources including servers, storage, databases, networking, and software services are owned and operated by a third-party cloud provider and made available to multiple organizations and individuals over the internet on a shared, multi-tenant infrastructure basis. Public cloud resources are provisioned on demand, billed based on consumption, and managed by the provider, with customers accessing those resources without owning or physically controlling any underlying hardware.
Amazon Web Services (AWS), Microsoft Azure, and Google Cloud Platform (GCP) are the dominant public cloud providers globally, collectively operating thousands of data centers across hundreds of geographic regions and serving organizations ranging from startups to the world’s largest enterprises.
Defining Characteristics of Public Cloud
- Multi-tenancy: multiple customers share the same underlying physical infrastructure, isolated from each other through virtualization and logical separation
- On-demand self-service: resources can be provisioned and decommissioned by customers without human interaction with the provider
- Broad network access: resources are accessible from any location with internet connectivity
- Rapid elasticity: capacity scales up and down on demand, automatically or manually, to match workload requirements
- Measured service: usage is monitored, controlled, and billed based on actual consumption
Public Cloud Security and the Shared Responsibility Model
Public cloud security operates under a shared responsibility model that divides security obligations between the provider and the customer. The provider secures the physical infrastructure, hypervisor layer, and global network. The customer is responsible for securing what they build and deploy on that infrastructure: operating system configuration, application security, identity and access management, data encryption, and network security group rules.
Misunderstanding the shared responsibility boundary is a primary cause of cloud security incidents. Customers who assume the cloud provider secures all layers often leave their own configurations dangerously exposed.
Public Cloud vs. Private and Hybrid Cloud
Public cloud offers the greatest scalability, the broadest service catalog, and the lowest barrier to entry. Private cloud provides dedicated infrastructure with greater control but higher operational cost. Hybrid cloud combines both, enabling organizations to match each workload to the most appropriate environment based on performance, compliance, and cost requirements.
Key Takeaways
- The public cloud delivers shared, multi-tenant computing resources over the internet managed by third-party providers.
- AWS, Azure, and GCP are the dominant providers, offering global infrastructure across hundreds of geographic regions.
- Public cloud is characterized by on-demand provisioning, elastic scaling, and consumption-based billing.
- The shared responsibility model defines which security obligations belong to the provider and which belong to the customer.
- Misunderstanding shared responsibility is a leading cause of cloud security misconfiguration incidents.