Understanding Cloud Computing: IaaS, PaaS, SaaS, and the Shared Responsibility Model

Cloud computing facilitates the convenient and on-demand utilization of computing resources like networks, servers, storage, applications, and services via network connectivity. It allows faster deployment of applications and services, essential in experimental and early development stages.

The Shared Responsibility Model

A critical concept in cloud computing is the Shared Responsibility Model, which defines the division of responsibilities between the cloud service provider and the customer. The allocation of these responsibilities depends on the type of service model being used:

  • In some cases (e.g., IaaS), the provider manages physical infrastructure, while the customer configures and secures the virtual environment.
  • In others (e.g., SaaS), the provider assumes responsibility for almost all operational aspects, and the customer’s role is largely limited to managing data and user access.
cloud models and shared responsibility

The Three Primary Service Models

While additional service models now exist—such as Function as a Service (FaaS), Data as a Service (DaaS), and Database as a Service (DBaaS)—cloud computing is most commonly categorized into three primary models, distinguished by the degree of user management required: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

  1. Infrastructure as a Service (IaaS)

IaaS provides fundamental infrastructure components—such as virtual machines, networking, and storage—without requiring customers to manage physical hardware. This model offers significant flexibility and control over operating systems, applications, and configurations. It leaves system and application-level management in the customer’s hands.

Examples: Amazon EC2, Google Compute Engine, Microsoft Azure Virtual Machines.

  1. Platform as a Service (PaaS)

PaaS builds upon IaaS by abstracting most infrastructure management tasks. It offers a ready-to-use platform for developing, testing, and deploying applications without the need to manage operating systems, runtime environments, or scaling concerns. Developers can focus on application logic while relying on the provider for infrastructure reliability and performance.

Examples: AWS Elastic Beanstalk, Google App Engine, Azure App Service.

  1. Software as a Service (SaaS)

SaaS delivers complete, ready-to-use applications over the internet. The provider manages all underlying infrastructure, middleware, and updates, while users simply access the service via a web browser or application interface. This model eliminates the need for installation, maintenance, or direct infrastructure oversight.

Examples: Gmail, Microsoft 365, Slack, Zoom.

Key Advantages of Cloud Computing

  • No limited capacity of hardware: one of the primary drawbacks of on-premise solutions is the finite capacity of hardware. This limitation directly impacts the number of users who could simultaneously connect to and utilize the server resources.

  • Delegated maintenance of the servers: cloud service provider takes care of maintaining servers, and splits the operational costs among multiple customers. Software updates and licensing are fully managed by the cloud service provider, ensuring that update-related server downtime does not impact the availability or performance of running applications.

  • Elastic scalability: Automated scaling mechanisms and load balancing facilitate seamless adaptation to fluctuating user demand, reducing the risk of performance degradation under peak load conditions.

  • Geographically distributed deployment: Multi-region hosting capabilities minimize network latency and improve availability by serving content from locations geographically proximal to end users.

Summary

Cloud computing gives engineering teams the flexibility to build, deploy, and scale applications without the friction of managing physical infrastructure. Whether you’re working with IaaS for full control, PaaS for streamlined deployment, or SaaS for ready-to-use tools, understanding the shared responsibility model ensures you know exactly what’s in your domain.

For software engineers, this means faster delivery cycles, easier experimentation, and infrastructure that adapts as quickly as your codebase evolves. You get to spend more time solving user problems and less time managing low-level infrastructure.

📚 References & further reading

Achieving Reproducibility in Cloud Benchmarking: A Focus on FaaS Services