Comment by toast0

When I was at yahoo, we certainly had load balancers, but we didn't have super fancy load balancers that could separate traffic out by path, so each 'property' would use a different hostname (i worked on travel.yahoo.com, which is dead these many years), but we all shared a login cookie (and some other cookies).

We'd have certainly adapted if we couldn't share cookies, but it would have been a lot messier.