Need someone experienced in web/database scaling [OFF]

Apologies in advance for the somewhat off-topic post. This is quite a
sophisticated group so it strikes me as the right group of people to ask.

I'm trying to find someone experienced in scaling open-source,
database-backed web applications. Particularly, I have an application based
on Linux-Apache-PHP-Postgres, that my customer would like to scale to
support 500 simultaneous users (by which they do mean 500 simultaneous
submits, since the app gets used that way).

I'd like to find someone who has done this, minimally with Apache and other
middleware + db, ideally with PHP and more ideally with PHP-postgres. I need
it to be someone who has actually done it, as opposed to someone with a
theoretical knowledge of how it should be done.

If you are such a person, or you know of one, can you please email me
offline at slane(at)moyegroup(dot)com?

-- sgl