what exactly do you mean by ‘concurrency’ ?

F#’s async workflows are supported.

Not sure how this is implemented behind the covers - I guess it get’s compiled to JS promises.

Yes - F# provides its own async model via an `async` computation expression. But you can also use the TPL in .NET BCL. F# 6 will have native support for TPL via a `task` computation expression.

But honestly, its own async model is great - arguably better than TPL for business systems. It sacrifices a little top-end performance/power and in return you get a supremely clean abstraction.