This is a tutorial on how to build a serverless round robin call forwarding application using Twilio Studio and Functions. The application allows for seamless call routing among multiple numbers, with the ability to reset or increment the counter variable as needed. The solution utilizes Twilio's Runtime suite, including Twilio Studio and Functions, to create a fully managed and scalable system without the need for a web server. The tutorial covers the prerequisites, installation of required modules, creation of a serverless counter variable, deployment of a Twilio Function, and configuration of a Studio Flow to trigger the function. The application is designed to be flexible and can be easily modified or extended to accommodate different use cases.