Cloud computing provides developers and IT departments with the ability to  focus on what matters most and avoid undifferentiated work such as  procurement, maintenance, and capacity planning. As cloud computing has  grown in popularity, several different models and deployment strategies have  emerged to help meet specific needs of different users. Each type of cloud  service and deployment method provides you with different levels of control,  flexibility, and management. Understanding the differences between  Infrastructure as a Service, Platform as a Service, and Software as a Service,  as well as what deployment strategies you can use, can help you decide what  set of services is right for your needs. 

Cloud Computing Models 

Infrastructure as a Service (IaaS) 

Infrastructure as a Service (IaaS) contains the basic building blocks for cloud IT  and typically provides access to networking features, computers (virtual or on  dedicated hardware), and data storage space. IaaS provides you with the  highest level of flexibility and management control over your IT resources and is  most similar to existing IT resources that many IT departments and developers  are familiar with today. 

Platform as a Service (PaaS) 

Platform as a Service (PaaS) removes the need for your organization to  manage the underlying infrastructure (usually hardware and operating systems)  and allows you to focus on the deployment and management of your  applications. This helps you be more efficient as you don’t need to worry about  resource procurement, capacity planning, software maintenance, patching, or  any of the other undifferentiated heavy lifting involved in running your  application. 

Software as a Service (SaaS) 

Software as a Service (SaaS) provides you with a completed product that is run  and managed by the service provider. In most cases, people referring to  Software as a Service are referring to end-user applications. With a SaaS  offering you do not have to think about how the service is maintained or how the underlying infrastructure is managed; you only need to think about how you will  use that particular piece of software. A common example of a SaaS application  is web-based email which you can use to send and receive email without  having to manage feature additions to the email product or maintain the servers  and operating systems that the email program is running on. 

Cloud Computing Deployment Models 

Cloud 

A cloud-based application is fully deployed in the cloud and all parts of the  application run in the cloud. Applications in the cloud have either been created  in the cloud or have been migrated from an existing infrastructure to take  advantage of the benefits of cloud computing. Cloud-based applications can be  built on low-level infrastructure pieces or can use higher level services that  provide abstraction from the management, architecting, and scaling  requirements of core infrastructure. 

Hybrid 

A hybrid deployment is a way to connect infrastructure and applications  between cloud-based resources and existing resources that are not located in  the cloud. The most common method of hybrid deployment is between the  cloud and existing on-premises infrastructure to extend, and grow, an  organization’s infrastructure into the cloud while connecting cloud resources to  the internal system. For more information on how AWS can help you with your  hybrid deployment, please visit our hybrid page. 

On-premises 

The deployment of resources on-premises, using virtualization and resource  management tools, is sometimes called the “private cloud.” On-premises  deployment doesn’t provide many of the benefits of cloud computing but is  sometimes sought for its ability to provide dedicated resources. In most cases  this deployment model is the same as legacy IT infrastructure while using  application management and virtualization technologies to try and increase  resource utilization.