Cloud computing

Cloud computing is the on-demand delivery of computing resources over the internet, enabling users to access and use shared pools of configurable infrastructure, platforms, and software without owning or directly managing the underlying physical hardware. The term gained widespread adoption following Amazon Web Services' launch of its Elastic Compute Cloud (EC2) service in 2006, though the conceptual roots of shared computing resources date to the mainframe computing era of the 1960s.

History and origins

The foundational idea of computing as a utility was articulated as early as 1961, when computer scientist John McCarthy suggested at an MIT centennial that computing might one day be organised as a public utility. Throughout the 1990s, telecommunications companies began offering virtualised private network services at reduced costs, which represented an early step toward the cloud model.

The phrase cloud computing became commercially significant in 2006, when Amazon introduced EC2 and Google CEO Eric Schmidt used the term at an industry conference. Amazon Web Services (AWS) is widely credited with popularising the infrastructure-as-a-service model on a commercial scale. Microsoft launched Microsoft Azure in 2010, and Google Cloud Platform became a major competitor in subsequent years, solidifying what became known as the hyperscaler market.

The National Institute of Standards and Technology (NIST) published an influential formal definition in 2011 (Special Publication 800-145), which identified five essential characteristics, three service models, and four deployment models that remain the canonical framework for describing cloud computing.

Core characteristics

NIST's definition identifies five essential characteristics of cloud computing:

• On-demand self-service: Users can provision computing capabilities automatically without requiring human interaction with the service provider.
• Broad network access: Capabilities are available over the network and accessed through standard mechanisms supporting diverse client platforms.
• Resource pooling: Provider resources are pooled to serve multiple consumers using a multi-tenant model, with physical and virtual resources dynamically assigned.
• Rapid elasticity: Capabilities can be elastically provisioned and released, often automatically, to scale with demand.
• Measured service: Resource usage is monitored, controlled, and reported, providing transparency for both provider and consumer.

Service models

Infrastructure as a Service (IaaS)

In the Infrastructure as a Service (IaaS) model, a provider delivers virtualised computing infrastructure—servers, networking, and storage—over the internet. Customers manage operating systems, middleware, and applications while the provider maintains the physical hardware. AWS EC2, Microsoft Azure Virtual Machines, and Google Compute Engine are prominent examples.

Platform as a Service (PaaS)

Platform as a Service (PaaS) provides a managed environment for developing, testing, and deploying applications. The provider controls the underlying infrastructure and runtime environment; customers focus on application code and data. Examples include Google App Engine, AWS Elastic Beanstalk, and Microsoft Azure App Service.

Software as a Service (SaaS)

Software as a Service (SaaS) delivers complete, ready-to-use applications over the internet, managed entirely by the provider. End users access these applications through a web browser or lightweight client. Widely used SaaS products include Google Workspace, Microsoft 365, Salesforce, and Dropbox.

Emerging models

Additional service models have emerged as the industry has matured, including Function as a Service (FaaS), also known as serverless computing, in which providers run individual functions in response to events and charge only for execution time. Database as a Service (DBaaS) abstracts database management into a managed service, and Container as a Service (CaaS) platforms such as Kubernetes-based offerings manage containerised workloads.

Deployment models

Public cloud

In a public cloud deployment, infrastructure is owned and operated by a third-party provider and shared among multiple tenants. Resources are delivered over the public internet. This model offers the greatest economies of scale and the lowest upfront capital expenditure.

Private cloud

A private cloud is dedicated exclusively to a single organisation, hosted either on-premises or by a third party. It offers greater control, customisation, and isolation, which is important for organisations with strict regulatory or security requirements.

Hybrid cloud

A hybrid cloud combines public and private cloud environments, with orchestration between the two. Organisations use hybrid deployments to keep sensitive workloads on-premises while leveraging public cloud scalability for less sensitive operations.

Multi-cloud

A multi-cloud strategy involves using services from two or more cloud providers to avoid vendor lock-in, optimise costs, or match specific workloads to the provider best suited for them. Analysts have noted that multi-cloud adoption has grown substantially among large enterprises, though specific adoption statistics vary by source and year of survey.

Security and compliance

Cloud computing introduces a shared responsibility model for information security: the provider secures the underlying infrastructure, while the customer is responsible for securing data, identity management, and application configuration. Misconfigurations of cloud storage buckets and insufficient identity controls have been documented as frequent causes of data breaches.

Regulatory frameworks such as the EU General Data Protection Regulation (GDPR), the US Health Insurance Portability and Accountability Act (HIPAA), and various national data-residency laws impose requirements on where data may be stored and how it must be protected, directly influencing cloud architecture decisions. Major providers offer compliance certifications including ISO/IEC 27001, SOC 2, and FedRAMP (in the United States government context).

Environmental impact

Data centres powering cloud services consume significant quantities of electricity and water for cooling. Providers including AWS, Google, and Microsoft have made public commitments to matching or exceeding their energy consumption with renewable sources, though the precise environmental benefit of cloud migration compared to on-premises infrastructure depends on the efficiency of the replaced systems and the energy mix of the region. The topic remains an active area of research and policy discussion.

Economic impact

Cloud computing has materially lowered the barrier to entry for technology-intensive businesses by replacing large capital expenditure on hardware with operational expenditure scaled to usage. This shift enabled the rapid growth of software start-ups in the 2010s, as companies could scale globally without building their own data centres. Conversely, some organisations performing stable, predictable workloads at scale have found that repatriating workloads to owned infrastructure (sometimes called cloud repatriation) reduces long-term costs, indicating that the economic calculus is not universally in favour of public cloud for all use cases.

Frequently asked questions

Is cloud computing the same as the internet?

Cloud computing is not synonymous with the internet; it refers to a specific model of delivering computing resources as a service over networks, including the internet. The internet is the underlying network infrastructure that makes public cloud services broadly accessible.

Is cloud computing secure?

Cloud computing can be highly secure when configured correctly, but security depends on both the provider's controls and the customer's own configuration and access management practices. Misconfigurations and weak identity controls remain common sources of cloud-related security incidents.

Is serverless computing a form of cloud computing?

Serverless computing is a subset of cloud computing in which the provider dynamically manages infrastructure allocation and charges customers only for the resources consumed during function execution, abstracting server management entirely from the developer.

Is cloud computing suitable for all workloads?

Cloud computing is well-suited to variable, bursty, or rapidly scaling workloads, but some organisations with stable, high-volume, predictable workloads have found dedicated on-premises infrastructure more cost-effective. The appropriate deployment model depends on an organisation's specific technical, regulatory, and financial requirements.

Is data stored in the cloud always in one physical location?

Data stored in the cloud is typically distributed across multiple physical data centres, often in multiple geographic regions, to ensure availability and resilience. Providers offer configurable data-residency options to meet regulatory requirements that restrict cross-border data transfers.