Serverless/FaaS is a generic computing model. Therefore, it would be possible to implement virtually any kind of workloads using this programming paradigm. The use cases of serverless/FaaS could range from an API for normal web applications, a RESTful backend for mobile applications, a function for log or video processing, a backend for WebHook-based systems, to a stream data processing program:

In Chapter 8, Putting Them all Together, we will discuss a system, as shown in the previous diagram, with the following use cases:

• APIs for a WebHook-based system: In the previous diagram, you may have spotted the Backend for UI. This system allows us to define a WebHook and it will be implemented as a FaaS function using one of the frameworks discussed in a later chapter.
• APIs to wrap around a legacy system: In the upper right-hand corner of the previous diagram, we will find a set of functions connecting to a Chrome Headless (a fully-functional running Google Chrome instance). The function there wraps around a set of commands to instruct Google Chrome to work on a legacy system for us.
• APIs as abstractions for other services: In the lower right-hand corner there are two simple blocks. The first one is a function running on a FaaS platform connecting to the second one, Mock Core Bank System, which is a more complex REST API. This part of the system demonstrates how a FaaS function could be used as an abstraction to simplify the interface of a complex system.
• Stream data processing: We will also implement a data processing agent, an event listener, which listens to an event source—you may find the Ethereum logo there with a circle that connects from the left. This agent will listen to the data stream from the source and then call a function running on a FaaS platform.