A Structured Literature Review Approach to Define Serverless Computing and Function as a Service

Nearly a decade ago, the emergence of an event-driven computing model attracted a lot of attention in industry and academia. This new computing concept has been described with a plethora of terms: Serverless Computing, Function as a Service (FaaS), Serverless functions, cloud functions, server-aware vs. server-less, to name only a few of the most frequently used terms. This enumeration showcases a problem of the domain: the lack of clear terminology, a conceptualization of Serverless and FaaS and a differentiation of the two. To overcome this limitation we present a Structured Literature Review (SLR) and usage trends which help to understand the current usage of the terms. Based on characteristics extracted from several definitions and validated in the course of the SLR we demarcate Serverless and FaaS. Our SLR shows that 90% of the considered papers predomi-nantly use the term Serverless whereas most of the authors intend to write about FaaS in the sense of our definition. Another insight is that the viewpoint on Serverless and FaaS evolved over time and that since 2021 most authors see Serverless as an umbrella term for FaaS and Backend as a Service (BaaS). Some of them also include further cloud service models, i.e. parts of PaaS and SaaS, providing a server-less experience for an application developer. This is an interpretation we share.