Cloud education

What is FaaS? Function as a Service explained

Brittany King

Posted: February 1, 20225 min read

Serverless computing allows developers to build and run applications without having to manage cloud infrastructure. There are still servers in serverless, but they are abstracted away from app development. Using a serverless model a cloud provider handles the routine work of provisioning, maintaining, and scaling the server infrastructure and developers can focus on code for deployment.

Function as a Service (FaaS) and serverless are often referred to synonymously, but they actually have two specific definitions. While serverless refers to any category where the server is fully abstracted from the end-user, FaaS is a subset of serverless computing that’s focused on event-driven triggers where code runs in response to events or requests. If there is no event-driven request, the server shuts down, making its resources available for other requests. Once deployed, FaaS responds to demand and automatically scales up and down as needed. Typically, when a serverless function is sitting idle, it doesn’t cost anything, saving money in many situations.

The relationship between IaaS, PaaS, and FaaS

Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and FaaS are all cloud computing offerings. The difference between them is the level of abstraction they provide between the user and the infrastructure.

IaaS offers the lowest level of abstraction. With IaaS, users have complete control over their infrastructure and the software and tools associated with their tech, but they don’t have to control or manage the physical infrastructure, like bare metal servers or data centers. IaaS gives developers the opportunity to choose the layers of abstraction they want. They can choose to manage everything, or they can layer in features such as load balancers or even managed services including Managed Kubernetes or Managed Databases to make maintaining their application easier.

PaaS adds another layer of abstraction for the end-user. With PaaS, users no longer have to manage the operating system, runtime, or other infrastructural components of their application, but will still have granular control over underlying application and infrastructure configurations. PaaS provides a fully managed infrastructure solution for developers looking to launch applications quickly. When developers choose to use PaaS, they can focus on their development work and let the provider manage backend services and system administration.

Of the three, FaaS offers the most abstraction for the user and the most specific functionality. With FaaS, developers have access to a platform that executes application logic on demand, and all of the application resources and other infrastructural components are managed by the service provider.

FaaS vs. PaaS

While FaaS and PaaS offerings initially seem quite similar, there are key differences to consider when deciding which is right for you.

  • Configuration. Because of its straightforward use case and completely managed solutions, FaaS offers extremely low provisioning time. Even though PaaS offers more abstraction than other cloud computing models, it still requires some configuration. This can be a benefit or a downside depending on the level of control you desire.
  • Operations. FaaS technologies spin entire applications up and down for individual requests. While PaaS has the ability to automatically scale up and down as needed, there are generally always resources running. This feature of FaaS can affect latency, pricing, and the ability to handle complex requests.
  • Scalability. PaaS does scale up and down as needed, but it requires thought and configuration from the developer. FaaS doesn’t require any capacity planning. It scales readily and easily as required.
  • Pricing. PaaS has different pricing models depending on your provider but is often more costly than FaaS if you’re running a low workload. FaaS allows developers to pay per function invocation, saving time if event triggers are few. PaaS may be the better option for consistent or high workloads in terms of pricing.

How FaaS works

Early applications were typically written using a monolithic architecture. This meant that the application was structured as a single execution that had to be triggered all at once. Over time, developers have increasingly shifted to using microservices. Microservices are a collection of modules that are independently deployable. Because they can be worked on individually, they are easier to test and maintain.

A function is essentially a microservice that can only perform one action in response to an event. With FaaS, the provider will spin up a server when a function is triggered. It will execute the function, then shut down the server. Serverless offerings are only active when the function is being used, allowing the same computing resources to be allocated elsewhere when the server is shut down.

Developers using FaaS have access to a platform that allows them to execute the code for their applications. Simplicity is the strong suit of FaaS. In order to use FaaS to the best of its ability, developers must ensure that each function only performs one action. The scope of the function should be limited and efficient. Using too many libraries or asking one function to call another function will quickly slow down the application and increase costs.

Benefits of FaaS

There are many benefits to using FaaS architecture. A few reasons you may choose to use FaaS for your application are:

  • The ability to focus solely on coding and development for your application
  • Cost savings by paying for only what you use
  • The ability to auto-scale without capacity planning or ongoing maintenance
  • Faster time to market due to the ease of development and testing

Considerations when choosing FaaS

FaaS can be used in a variety of ways, from web apps, data processing, and online chatbots to backend functions and more. Before committing to a FaaS provider, consider the following:

Workloads. Choose FaaS for simple and repetitive functions without consistent workloads or high volumes of requests. Because FaaS is typically priced per function execution, costs for high usage could potentially be higher than using a PaaS offering. If your workload is relatively small, FaaS is a great choice for simplifying provisioning and saving money.

Control. FaaS is one of the most abstracted cloud offerings. Consider the amount of insight and control you prefer over your configurations and infrastructure. If you want a bit more control than FaaS offers while maintaining similar ease of use, try a PaaS solution. Teams that want complete control over their production environment and the design and behavior of their infrastructure should consider using an IaaS solution.

Vendor lock-in. It can be challenging to migrate applications built through providers. Using open-source cloud solutions makes it easier to migrate computing operations from one provider to another.

DigitalOcean and Nimbella have joined forces to make serverless computing more accessible.

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