[burel]

here an article about various techniques to make github (a rails app) fast:

http://github.com/blog/530-how-we-made-github-fast

very interesting but also full of intimidating stuff:

"[...] For requests to the main website, the load balancer ships your request off to one of the four frontend machines. Each of these is an 8 core, 16GB RAM bare metal server. Their names are fe1, …, fe4. Nginx accepts the connection and sends it to a Unix domain socket upon which sixteen Unicorn worker processes are selecting. One of these workers grabs the request and runs the Rails code necessary to fulfill it. [...]"

I think they know what they are doing ...