which version nopCommerce used in nopcommerce.com official site ?

which version of nopCommerce used in nopcommerce.com official site ? we use last version of nopcommerce site but we have problem in server when online users around 100 but nopcommerce official site has online users some time around +1000 which version is used ? or which performance optimisations made?

nopCommerce 1.90

thank you ,  we also move back 3 web site this week from nop 3.2  to  nop 1.9 because of performance complain problems, nop 1.9 work better than new nop version 3.2 and nop 1.9 keep 10 times more online users with same memory usage 3.2 version