Most web servers are bottlenecked on Io and memory. Assuming the bottleneck is that your app servers are starved for more data ( as opposed to trying to push o

Most web servers are bottlenecked on Io and memory. Assuming the bottleneck is that your app servers are starved for more data ( as opposed to trying to push out too much data to clients,) then a big part of your request cycle is waiting. Waiting for db, waiting for memcache, waiting for web service, waiting for disk to return some file, etc. The other thing is that your app servers will gobble ram. This is less true with copy on write, but ruby implementations and rails are usually very memory hungry. Node is not. Node is more like rack than rails, so it isn't fair to compare the two.