Serverless has a free tier. Every example of it that I've seen has been much faster than the other free tier options. If you run one locally, you'll see some key difference between using a Chrome and Firefox web driver. Every time a function with an external call is made Chrome will start a new process, regardless of your local environment. These process remain open until the call returns. Firefox on the other hand will manage them all as one process. The determination of when something gets pushed to page file is ultimately determined by the system, as is the management of threads. However, Chrome's method generally takes up more ram, opens more simultaneous threads, and performs better.