There is a nice project on authentication started by Tobias here:
it is a nice survey and a nice start!
Also about performance issues on symfony2 regarding doctrine2 this is another interesting reading
I would actually be more interested in reading about “There are many more factors, like network load, inefficient database indices or no indices, and much more. Don’t just always look at the raw execution speed of your code. ”
examples of inefficient db indices or no indices etc, regarding my model here http://img6.imagebanana.com/img/hwshoaju/Selection_004.png
if there is any inefficiency I would like to correct it at the earliest