Ye Gods! Just looked at the stats for Tumblr.

500 million page views a day

15B+ page views month

~20 engineers

Peak rate of ~40k requests per second

1+ TB/day into Hadoop cluster

Many TB/day into MySQL/HBase/Redis/Memcache

Growing at 30% a month

~1000 hardware nodes in production

Billions of page visits per month per engineer

Posts are about 50GB a day. Follower list updates are about 2.7TB a day.

Dashboard runs at a million writes a second, 50K reads a second, and it is growing.

And all this with about twenty engineers!