For a post titled "How Ravelry Scales to 10 Million Requests Using Rails" the only scaling advice they mention are the technical specs of the site like:
Tokyo Cabinet/Tyrant is used instead of memcached in some places for caching larger objects. Specifically markdown text that has been converted to HTML.
and this one tip:
The database is the problem. Nearly all of the scaling/tuning/performance related work is database related. For example, MySQL schema changes on large tables are painful if you don’t want any downtime. One of the arguments for schemaless databases.
It should be illuminating that a site of this size doesn't need to have a lavish description of arcane scaling strategies. It's fairly straightforward so the how they make the site becomes most interesting.
Tokyo Cabinet/Tyrant is used instead of memcached in some places for caching larger objects. Specifically markdown text that has been converted to HTML.
and this one tip:
The database is the problem. Nearly all of the scaling/tuning/performance related work is database related. For example, MySQL schema changes on large tables are painful if you don’t want any downtime. One of the arguments for schemaless databases.
Not much "how" in that.