The following diagram illustrates the position of event-driven programming, FaaS, and serverless FaaS, where serverless FaaS is the intersection area between FaaS and serverless:
Serverless is a paradigm shift that enables developers to not worry about server provisioning and operations. Billing would be pay-per-request. Also, many useful services are there on the public cloud for us to choose, connecting them together and use them to solve the business problems to get the job done.
Applications in the serverless architecture typically use third-party services to do other jobs such as authentication, database systems, or file storage. It is not necessary for serverless applications to use these third-party services, but architecting the application this way takes full advantage of the cloud-based serverless platforms. The frontend applications in this kind of architecture are usually a thick, fat, and powerful frontend, such as single-page applications or mobile applications.
The execution engine for this serverless computing shift is a Function as a Service or FaaS platform. A FaaS platform is a computing engine, that allows us to write a simple, self-contained, single-purpose function to process or compute a task. A compute unit of a FaaS platform is a function that is recommended to be stateless. This stateless property makes functions fully manageable and scalable by the platform.
A FaaS platform does not necessarily run on a serverless environment, such as AWS Lambda, but there are many FaaS implementations, such as OpenFaaS, the Fn Project, and OpenWhisk, that allow us to deploy and run FaaS on our own hardware. If a FaaS platform runs in the serverless environment, it would be called serverless FaaS. For example, we have OpenWhisk running locally, so it is our FaaS platform. But when it is running on IBM Cloud as IBM Cloud Functions, it is a serverless FaaS.
Every FaaS platform has been designed to use the event-driven programming model, to be able to connect efficiently to other services on the public cloud. With the asynchronous event model and the stateless property of functions, this environment makes serverless FaaS an ideal model for next-generation computing.