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Cloud Computing and Serverless Architectures: What are FaaS and CaaS?

8 min

When creating new cloud-native applications, developers need to choose the development and deployment methods that best serves their application's needs and purpose. At the same time, organizations are always looking to optimize their cloud budgets and efficiency.

Two popular deployment strategies are Function as a Service (FaaS) and Container as a Service (CaaS). Perhaps you've heard about them! In this blog post, we review what exactly are FaaS and CaaS, as well as cover their unique benefits and shortcomings, all before explaining how these services can be used in serverless architecture.

By comparing FaaS and CaaS in this blog post, we hope to empower newcomers and engineers alike to make the best decisions concerning the deployment of their applications.

Table of Contents

  1. Overview
  2. FaaS and CaaS Meaning
  3. More about Cloud Computing and Serverless
  4. Serverless FaaS and CaaS Platform Powered by Koyeb


Function as a Service (FaaS) is a hosting and deployment strategy where the underlying infrastructure is managed and scaled by the provider; the user only needs to provide the function code. FaaS is a good solution for simple tasks, APIs, and parallel and high-volume workloads, like media processing.

Container as a Service (CaaS) is also a hosting and deployment strategy, which instead of using functions as deployment unit, uses container technology. A container is a unit of software that packages an application's code, dependencies, and libraries, in a standard way, so that it can run anywhere regardless of the underlying infrastructure. CaaS is an excellent solution for those who are looking to move their applications between clouds and environments, a process which is also known as lift and shift.

FaaS and CaaS Meaning

First, it helps to understand the defining terms of these services:

  • A function is a block of code that executes a single, specific, task once triggered by an event.
  • A container is a unit of software that packages an application's code, dependencies, and libraries, in a standard way. Containers have been democratized by Docker, the leading container technology.

Faas and CaaS are both hosting and deployment strategies for applications, web projects, and APIs. Key differences between these services are their architectural designs, how they operate, and where they sit in the cloud computing ecosystem.

When coupled with serverless, the significant impact of the FaaS and CaaS models is that users no longer have to provision, manage, or scale the infrastructure they require. This is a transition away from the classic IaaS model with virtual machines that required users to manage load-balancing, scaling, and availability. Now cloud service providers handle these complexities and offer users resilient, high-performing, and autoscaling infrastructure.

FaaS and CaaS in Cloud Computing Pyramid

Here is a visual representation of where FaaS and CaaS fall in the traditional cloud computing pyramid.

FaaS: Function as a Service

FaaS is a dynamic, on-demand, type of cloud computing in which functions are triggered by an event or a request. With FaaS, the cloud service provider manages the underlying infrastructure, including the physical hardware, the operating system, and the runtime environment. All the user has to provide is the function code that will run and specify which events should trigger which functions.

FaaS is often confounded with serverless technology because FaaS is often implemented in serverless architectures.

  • Benefits: The FaaS model abstracts the runtime and container configurations to the end-user, reducing packaging complexity and knowledge required. It's basically a new simplification for the developer who can focus on developing new features. It also provides an increased deployment granularity allowing each function to be deployed and scaled independently. Serverless associated with the FaaS model optimizes costs and saves hours of manpower. These savings translate to faster time-to-market for your applications and projects. Moreover, cost granularity is an additional perk of Serverless FaaS as users are only charged for the time and power their functions use.

  • Drawbacks: Rewriting applications to conform to FaaS architectures is a considerable obstacle as most development frameworks are not designed for it, yet. Then, forfeiting the control of the runtime might generate significant challenges with package and system dependencies management. This is related to the fact that FaaS lacks standardization across cloud service providers and FaaS implementations are very cloud-specific so far; therefore, portability and vendor-locking become issues. Two additional critiques of the FaaS model include the possible introduction of debugging and testing challenges.

All in all, FaaS is a powerful and cost-effective way to run applications in the cloud. As for the risk of adding debugging and testing complexities, this is a matter of overcoming the learning curve of re-imagining how to code and test when building projects that will run as serverless functions. The FaaS ecosystem and tooling are also evolving at a fast pace, progressively bridging the gaps.

CaaS: Container as a Service

CaaS is a cloud computing model that enables users to host and deploy applications in containers. A container is a unit of software that packages an application's code, its dependencies, and libraries, in a standard way, so that it can run anywhere regardless of the underlying infrastructure.

Like traditional virtual machines, containers are isolated computing environments. However, containers are considerably more portable compared to virtual machines. While containers are more lightweight and their format is standardized thanks to the Open Container Initiative (OCI), virtual machines are much heavier and less standardized in comparison.

With CaaS, cloud service providers offer the containers and container orchestration platforms that allow users to create and manage their containers.

Let's look at the benefits and drawbacks:

  • Benefits: CaaS is a simple and efficient way to deploy applications. Since the operating system and system dependencies are embedded by design, container applications are incredibly portable and flexible. Consistency is a huge advantage of CaaS, it means containers can run with the same behavior regardless of the device or environment deploying them, from a developer's laptop to cloud platforms and edge devices. Moreover, containers scale easily and facilitate traceability.
  • Drawbacks: Criticism of the CaaS model includes the fact that CaaS platforms are not all serverless by design, which means orchestration and scaling is often the user's responsibility. Fortunately, CaaS can also be serverless. One of the challenges of CaaS is that it still requires some understanding of the runtime and containerization technology. Security and configuration of these two components are still the responsibilities of the platform's user.

Overall, CaaS streamlines development, making it a highly efficient and cost-effective solution for application deployment and hosting. The CaaS model is especially powerful combined with serverless platforms.

More about Cloud Computing and Serverless

Knowing the difference between FaaS and CaaS deployments, as well as their unique advantages and shortcomings, will help you when deciding how to design and launch your next application.

If you enjoyed learning about FaaS and CaaS, you may enjoy reading about:

Serverless FaaS and CaaS Platform Powered by Koyeb

Once you decide which deployment strategy you want to use for your application, combining these strengths with the advantages of a serverless platform will help optimize cloud budgets and increase your web app's efficiency.

Koyeb is the developer-friendly serverless platform to deploy container-based and function-based applications globally. Enjoy fast startup times and minimal overhead for each application you deploy all while no longer worrying about scaling or managing the underlying infrastructure of your app.

In addition to auto-scaling, the Koyeb serverless platform combines the flexibility of PaaS with the performance and security of MicroVMs. Get the security and isolation features required for data-sensitive applications without compromising on speed, security, and performance.

See the benefits of going serverless, get started with a free account today!

Here are some useful resources to get you started:

  • Koyeb Documentation: Learn everything you need to know about using Koyeb.
  • Koyeb Tutorials: Discover guides and tutorials on common Koyeb use cases and get inspired to create your own!
  • Koyeb Community: Join the community chat to stay in the loop about our latest feature announcements, exchange ideas with other developers, and ask our engineering teams whatever questions you may have about going serverless.

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