Yup, as of now we are leveraging Nodejs for the technical preview. We also have another preview using embedded v8 for inline transforms, that is your transform

Yup, as of now we are leveraging Nodejs for the technical preview. We also have another preview using embedded v8 for inline transforms, that is your transform runs in-process and apply() boils down to a function call. We are still evaluating other runtimes like wasmer as well, v8 was initially chosen for its maturity and community support.