IaaS, PaaS, and SaaS: The Differences Between the Three Cloud Service Models and Criteria for Choosing the Right One

The cloud is no longer simply a matter of "renting a server." Corporate IT strategy has shifted to a choice between how much direct control to maintain and how much to delegate. IaaS, PaaS, and SaaS are not simply technical terms; they are design philosophies that determine an organization's operational methods, development culture, and security strategy. A poor choice can reduce costs but actually increase complexity.

What is IaaS (Infrastructure as a Service)?

IaaS is a model that provides infrastructure, such as servers, storage, and networks, as a service. It allows you to build a data center-level environment without purchasing physical servers.

characteristic

• Direct management of OS, middleware, and applications
• High degree of freedom at the infrastructure level
• Maintain control over security, network, and scalability design.

Advantageous system types

• Companies that operate their own service platforms
• When migrating legacy systems to the cloud
• Systems with high security and compliance requirements
• Services with large traffic fluctuations

IaaS is not a choice to “get rid of servers,” but rather a choice to replace servers with software.

What is PaaS (Platform as a Service)?

PaaS is a model that provides the platform necessary for application development and execution. It allows you to focus on your code without worrying about server configuration, OS management, or runtime environments.

characteristic

• No need to manage infrastructure and runtime environment
• Rapid development and deployment cycle
• Specific platform dependencies may occur

Advantageous system types

• Development of new web and mobile services
• MVP and rapid prototyping
• Internal business applications
• Organizations with low DevOps maturity

PaaS is a choice that sacrifices some design freedom in exchange for maximizing development productivity.

What is SaaS (Software as a Service)?

SaaS is a model where finished software is used immediately. Users simply utilize the features, while the service provider is responsible for operations, security, and updates.

characteristic

• No installation or operation burden
• Quick introduction possible
• There are limitations to customization.

Advantageous system types

• Email, collaboration, CRM, ERP
• Marketing, Sales, and Customer Management Tools
• Accounting, HR, and Document Management Systems
• Organizations with limited IT personnel

SaaS is the most complete form of consuming IT as a service rather than an asset.

Differences at a glance

Strategic choices from a corporate perspective

• Core services/differentiated areas → IaaS
• New services/experimental projects → PaaS
• Non-core/standard tasks → SaaS

A realistic corporate IT structure doesn't rely on just one. A hybrid strategy of IaaS, PaaS, and SaaS is common. The key isn't "technology," but rather a separation of responsibilities that fits the nature of the business.

Problems that often arise from making wrong choices

• Costs skyrocket as businesses deploy IaaS for tasks that could be handled with SaaS.
• Dependence on PaaS makes it difficult to migrate to other clouds.
• Failure to respond to failures due to lack of operational personnel in IaaS environments.

The reason cloud strategies fail most often is not the technology itself, but the lack of selection criteria.

Insight Summary

• IaaS, PaaS, and SaaS are not technology steps, but models of distributed responsibility.
• The greater the degree of freedom, the greater the operational responsibility.
• The most dangerous attempt is to unify all systems into one model.
• “What should I directly control?” is the starting point of choice.