An Investigation of the Impact of Language Runtime on the Performance and Cost of Serverless Functions

Serverless, otherwise known as "Function-as-a-Service" (FaaS), is a compelling evolution of cloud computing that is highly scalable and event-driven. Serverless applications are composed of multiple independent functions, each of which can be implemented in a range of programming languages. This paper seeks to understand the impact of the choice of language runtime on the performance and subsequent cost of serverless function execution. It presents the design and implementation of a new serverless performance testing framework created to analyse performance and cost metrics for both AWS Lambda and Azure Functions. For optimum performance and cost management of serverless applications, Python is the clear choice on AWS Lambda. C# .NET is the top performer and most economical option for Azure Functions. NodeJS on Azure Functions and .NET Core 2 on AWS should be avoided or at the very least, used carefully in order to avoid their potentially slow and costly start-up times.