PaaS vs. IaaS vs. SaaS vs. CaaS: How are they different?

You’re probably already aware of the potential of cloud computing to transform your organization. As you explore moving away from self-managed on-premises IT solutions, it’s important to understand the different options available to you when it comes to cloud computing services.

Looking to learn more about cloud IaaS, PaaS, SaaS, and CaaS? We’ll break down what you need to know about these major cloud computing service models, including what they mean in practice and how they are different from each other.

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What are IaaS, PaaS, SaaS, and CaaS?

Cloud computing has three main cloud service models: IaaS (infrastructure as a service), PaaS (platform as a service), and SaaS (software as a service). You might also hear IaaS, PaaS, and SaaS called cloud service offerings or cloud computing categories, but all of these terms refer to how you use the cloud in your organization and the degree of management you’re responsible for in your cloud environments.

In addition to these three broad categories, you may also come across other types of cloud services that incorporate other technologies, such as containers. For example, the rising adoption of containers and microservices architectures has led to the emergence of CaaS (containers as a service).

“As a service” typically means that the service model is offered by a third party in the cloud. In other words, you don’t have to purchase, manage, or use any hardware, software, tools, or applications from an on-premises data center. Instead, you can simply pay a subscription or pay based on consumption (pay-as-you-go) to access what you need on demand via an internet connection.

But what is IaaS, PaaS, SaaS, and CaaS exactly and what does each model offer you and your teams?

Here’s a basic breakdown of each service model:

IaaS

Infrastructure as a service, or IaaS, delivers on-demand infrastructure resources to organizations via the cloud, such as compute, storage, networking, and virtualization. Customers don’t have to manage, maintain, or update their own data center infrastructure, but are responsible for the operating system, middleware, virtual machines, and any apps or data.

CaaS

Containers as a service, or CaaS, delivers and manages all the hardware and software resources to develop and deploy applications using containers. Sometimes viewed as a subset or an extension of IaaS, CaaS uses containers rather than VMs as its main resource. Developers and IT operations teams can use CaaS to develop, run, and manage applications without having to build and maintain the infrastructure or platform to run and manage containers. Customers still have to write the code and manage their data and applications, but the environment to build and deploy containerized apps is managed and maintained by the cloud service provider.

PaaS

Platform as a service, or PaaS, delivers and manages all the hardware and software resources to develop applications through the cloud. Developers and IT operations teams can use PaaS to develop, run, and manage applications without having to build and maintain the infrastructure or platform on their own. Customers still have to write the code and manage their data and applications, but the environment to build and deploy apps is managed and maintained by the cloud service provider.

SaaS

Software as a service, or SaaS, provides the entire application stack, delivering an entire cloud-based application that customers can access and use. SaaS products are completely managed by the service provider and come ready to use, including all updates, bug fixes, and overall maintenance. Most SaaS applications are accessed directly through a web browser, which means customers don’t have to download or install anything on their devices.

Key differences between cloud IaaS, PaaS, SaaS, and CaaS

Understanding the difference between IaaS, PaaS, SaaS, and CaaS in cloud computing comes down to the level of control and responsibility. Each model offers an alternative to managing your own on-premises data center, but the service provider will manage different elements in the computing stack depending on which type you choose.

The diagram below shows how IaaS, PaaS, SaaS, and CaaS compare in terms of who is responsible for managing what:

Different cloud computing models and service structures

To understand cloud and the different models to choose from, it can help to think about it in terms of housing:

On-premises: If you decide to build your house from scratch, you do everything yourself. You’ll need to source the raw materials and tools, put everything together, and run to the store every time you need anything. This is similar to running an application on-premises, where you own everything from the hardware to your applications and scaling.
Infrastructure as a service: If you are busy, you might consider hiring a contractor to do the work. You tell them how you want the house to look and how many rooms you want, and they take the instructions and build your home. IaaS works in a similar way for your applications. You rent the hardware to run your application on, but you are responsible for managing the OS, runtime, scale, and all the data. Example: Compute Engine
Containers as a service: If buying a home is just too much work due to the maintenance it comes with, you can choose to rent instead. The basic utilities are included, but you bring your own furniture and make the space yours. With containers, you can bring a containerized application, so you don't have to worry about the underlying operating system but still have control over scale and runtime. Example: Google Kubernetes Engine (GKE)
Platform as a service: If you don’t want to worry about furnishing your living space, you can rent a furnished house. PaaS lets you bring your own code and deploy it but leaves the server management and scaling up to the cloud provider. Examples: App Engine, Cloud Run
Function as a service: If you just need a small dedicated place to work away from your home, you can rent a desk in a coworking workspace. Similarly, FaaS allows you to build and deploy a small piece of code, or a function, that performs a specific task. The cloud provider adds scale if needed when a function executes. Example: Cloud Functions
Software as a service: Now, imagine you move into a finished house (rented or purchased), but you have to pay for upkeep, such as cleaning or lawn care. SaaS is the same—you pay to use a complete application for a specific purpose that is managed, maintained, and secured by the cloud provider, but you are responsible for taking care of your own data. Example: Google Workspace

Choosing which is right for you: pros and cons

When it comes to choosing whether cloud IaaS, PaaS, or SaaS is right for your business, there are different advantages and disadvantages to each service model.

In addition, it’s important to understand that all three are not mutually exclusive, where you can only choose a single service model. It’s possible to choose one for your needs, but you can also decide to combine it with another one or even use a mix of all three along with more traditional IT infrastructure.

Let’s take a look at some of the most common advantages and disadvantages for each model:

IaaS pros

Highest level of control over infrastructure
On-demand scalability
No single point of failure for higher reliability
Reduced upfront capital expenditures (for example, pay-as-you-go pricing)
Fewer provisioning delays and wasted resources
Accelerated development and time to market

IaaS cons

Responsible for your own data security and recovery
Requires hands-on configuration and maintenance
Difficulties securing legacy applications on cloud-based infrastructure

CaaS pros

Ideal for running, managing, and scaling microservices
Streamlined development speeds up time to market
More control and configuration of networks and application components
Increases workload portability between environments, such as hybrid cloud and multicloud
Built-in performance monitoring and container orchestration

CaaS cons

Some CaaS solutions have limited language support available depending on the cloud service provider
Container security risks may increase when using CaaS as they share the same kernel with the OS (although they are considered safer than VMs)

PaaS pros

Instant access to a complete, easy-to-use development platform
Cloud service provider is responsible for maintenance and securing infrastructure
Available over any internet connection on any device
On-demand scalability

PaaS cons

Application stack can be limited to the most relevant components
Vendor lock-in may be an issue depending on the cloud service provider
Less control over operations and the overall infrastructure
More limited customizations

SaaS pros

Easy to set up and start using
The provider manages and maintains everything, from hardware to software
Software is accessible over any internet connection on any device

SaaS cons

No control over any of the infrastructure or security controls
Integration issues with your existing tools and applications
Vendor lock-in may be an issue depending on the cloud service provider
Little to no customization

Google Cloud offers a wide range of IaaS, PaaS, SaaS, and CaaS solutions that you can choose from to create a cloud environment that meets your organization’s unique needs and requirements. Whether you’re looking to modernize existing applications, develop new cloud-native applications, or simply want ease of use and scalability, we provide products and solutions to help you achieve your goals and improve business outcomes.