I believe Activision uses an studio dedicated to multiplayer servers called Demonware: https://demonware.net/ https://demonware.net/ Maybe they have some infor

I believe Activision uses an studio dedicated to multiplayer servers called Demonware: https://demonware.net/ https://demonware.net/ Maybe they have some information on some of the methods they use, when googling for them (haven't searched myself)