When I left MS in late 00s, he was still in Bing. From what I heard Bing, ironically, _still_ doesn't use anything Azure and builds its own cloud infrastructure

When I left MS in late 00s, he was still in Bing. From what I heard Bing, ironically, _still_ doesn't use anything Azure and builds its own cloud infrastructure. :-) Exchange runs its own bespoke stuff, too. I suppose much like Google Search, Gmail and Ads don't use GCP, but worse, because at least Google has one offering internally and one externally, whereas MS has multiple.