Which service model is optimal for billing based on actual usage, particularly execution time?

The most suitable service model for billing based on actual usage, particularly in terms of execution time, is Function as a Service (FaaS). FaaS operates on a serverless model where users can deploy individual functions or pieces of code that run in response to events. With FaaS, billing is directly tied to the actual execution time of these functions, which means users only pay for the computing resources consumed while the code is actively running.

This model is particularly beneficial for applications with variable workloads or those that require scalability on demand. Because functions are triggered only when needed, FaaS allows organizations to optimize their costs by avoiding the expense of pre-allocating server resources that may not be in use continuously. The granularity of billing aligns precisely with usage patterns, making it ideal for services that need to manage costs effectively while maximizing efficiency.

In contrast, other options such as Software as a Service (SaaS) typically involve subscription-based pricing models that do not directly correlate cost with execution time. Infrastructure as Code (IaC) focuses primarily on the management of infrastructure using code for automation, rather than providing a usage-based billing mechanism. Software-Defined Networking (SDN) pertains to network management and is not directly related to application execution