When your applications have a reasonable number of UI (User Interface) tests, it is inevitable that you’ll want to have a solution to execute them concurrently, in order to achieve a faster feedback cycle. But there are shortfalls in using plain EC2 based Selenium Grid or SeleniumGrid running a data center, as we move to a micro-service world and towards a shift-left approach for testing. (Testing earlier in the development cycle, even before committing the code, to find and fix problems early.)