I was one of two developers on a social media network in Norway, at peak hours (from about 20:00 till 22:00) we had 60.000 unique users with activity within the last 10 minutes. This generated about 400 dynamic req/s and about 6000 static req/s. We managed this sustained traffic with a total of 12 webservers (apache + memcached), 4 databases (mysql) and 6 Varnishes.