Have you run any sorts of performance benchmarks on this?
I like async/await a lot, but I'm concerned at how much all of this JS machinery costs in terms of perf, especially compared to writing callback chains.
I haven't. It probably mostly depends on the JS engine and Promise implementation.
That said, it might be a good idea to hand-optimize that single hot loop, typing the Promise chain out yourself, or even using callbacks directly. It's impossible to beat that using an automated solution like this.
