The Cloud Stack: IaaS, PaaS and SaaS

Perhaps the most confusing part about cloud computing is that there is no singular, one-size-fits all definition. Instead, depending on what services you are describing and who you are talking to, the term “the cloud” can take on a variety of meanings.

Since there is no simple definition, the chore for cloud services providers has been to come up with an accurate and descriptive method of describing their service offerings. So instead of just saying that they offer a cloud solution, they now refer to their solution with terms such as:

  • Infrastructure as a Service (IaaS)
  • Platform as a Service (PaaS)
  • Software as a Service (SaaS)  

So what is IaaS, PaaS and SaaS?

Separately these terms each make up different layers of what is commonly referred to as the cloud computing stack – with IaaS serving as the base of the stack and SaaS sitting at the top of the structure:

Defining  the Cloud Computing Stack



  • No user software upgrades
  • Applications for end users
  • Web access for commercial software

When SaaS makes sense: SaaS is an on-demand application delivery model operated by a third-party provider. Known for low maintenance and implementation costs, SaaS solutions offer flexibility and scalability while allowing for wide scale application adoption and shorter deployment times



  • Development Platform
  • Provides all things related to the day-to-day hosting of applications (hardware, operating system, software, security)
  • Multi-tenant architecture where multiple concurrent users share the same development platform 

When PaaS makes Sense: With PaaS, you can host your applications in the cloud without the expense and hassle of building and maintaining an infrastructure. 



  • The hardware and software that powers it all – servers, storage, networks, operating systems
  • Resources are distributed as a service
  • Allows for rapid scaling of resources

When IaaS Makes Sense: As the foundation of your cloud computing stack, IaaS is responsible for powering and housing everything (i.e. your server, storage, network, and operating system) This eliminates the need for buying, operating and maintaining hardware.

Looking for more insights on cloud computing terms? Watch this brief animation for a detailed explanation of varying cloud solutions.