It's pronounced keɪ (from your link - The spelling quay, first appearing in the sixteenth century, follows modern French. As noted by the Oxford English Dictionary, third edition, the expected outcome of Middle English keye would be /keɪ/ in Modern English). Or key (with modern spelling).
We actually originally pronounced it as "kway" (the American pronunciation we had heard) but then had a saying we'd tell customers (when asked) of "pronounce it however you please, so long as you're happy using it!" :)
I know quay is a real word - it's not normally pronounced like "kway" but like "key". But only because enough people agree on that - that's what I mean by made up. The rules are just a majority agreement for both meaning and pronunciation.
My french speaking partner recently informed me the quay (pronounced key) meant something like ‘dock’ when we were discussing the Florida Keys, and suddenly everything fell into place!
