Edit: I called it Kway myself and googled it after getting puzzled looks from my UK peers. The referenced article says "key" is the older pronunciation but either is acceptable.
I asked Brandon Phillips (Then CoreOS CTO) on a call how they said it. He was quite frank it was pronounced "kway" and not "key", much to the chagrin of our Aussie coworker who still calls it "key". I've called it "kway" since.
I'm from the UK and when I first moved to London I pronounced Surrey Quays Surrey Kways until I was corrected, I pronounced Torquay and Newquay correctly but it never occurred to me to pronounce Surrey Kways Surrey Quays.
Disclaimer: Named, cofounded, and now engineering lead of Quay