Rails scales just fine - the problem is that it's just really expensive to do it. Here's some of our learnings: 1. Use query_trace to trace your DB calls and

Rails scales just fine - the problem is that it's just really expensive to do it. Here's some of our learnings: 1. Use query_trace to trace your DB calls and query_analyzer to automatically run EXPLAIN on each call: http://github.com/ntalbott/query_trace/tree/master http://github.com/ntalbott/query_trace/tree/master http://github.com/jeberly/query-analyzer/tree/master http://github.com/jeberly/query-analyzer/tree/master 2. Use our patches to mongrel proc_title to troubleshoot slow queries: http://asemanfar.com/Request-Queue-via-Mongrel-Proctitle http://asemanfar.com/Request-Queue-via-Mongrel-Proctitle 3. Don't use ActiveRecord. 4. Don't use any link or url helpers in Rails. 5. For that matter, don't use Rails. Rewrite your most hit components in something faster. I love Ruby, but the simple truth of it is that we'd be saving a couple of engineer's worth of money if we weren't on Rails.