I'm not sure I'd necessarily call ```promisifyAll()``` "blazing fast" but in all fairness it's a cost incurred up front and that's it so it's not that bad.
The call itself is relatively expensive, but as you say it's a one off call at startup time and the methods it produces are faster than explicit promisification using `new Promise`, they are blazing fast :)
I'm not sure I'd necessarily call ```promisifyAll()``` "blazing fast" but in all fairness it's a cost incurred up front and that's it so it's not that bad.