I would say that storing session keys is vanishingly unlikely and eliminates the benefit of PFS. Google probably spends millions of dollars a year in PFS additi

I would say that storing session keys is vanishingly unlikely and eliminates the benefit of PFS. Google probably spends millions of dollars a year in PFS additional handshake costs. Google then storing the session keys would be a little like the Dutch building an expensive dike and then knocking a big hole in it. If you want to store data like "user X searched for Porsche 911 GTS 0-60 statistics, so let's show him some 991 Cabriolet ads the next time we can," you don't need to store the session keys.