"APIs should be designed synchronously, and the callers should orchestrate concurrency if they choose" Just to add to this, I found the blog post he mentions[1

"APIs should be designed synchronously, and the callers should orchestrate concurrency if they choose" Just to add to this, I found the blog post he mentions[1] towards the bottom that supports this conclusion a really good read. [1] http://journal.stuffwithstuff.com/2015/02/01/what-color-is-your-function/ http://journal.stuffwithstuff.com/2015/02/01/what-color-is-y...