Is it a supercomputer? Or a couple of discount servers?
I think it is a “hired” average server!
They use Rackspace which is sort of middle of the road. From what I know it runs on four servers. A load balancer, two servers running Apache and one database server.
Two geriatric hamsters running (slowly) on a rusty wheel cobbled together with string & glue.
On the weekends I think @ucme is more spot on, this site gets stupid slow at responding during the weekends at least where I am from.