what is the efficient way to browse users by name?

I'm using mysql-php-memcached and I want to realize something lik开发者_运维知识库e that: http://www.facebook.com/directory/people/ to browse users by name.

Suppose I have hundred of thousands username, how can I handle it?

The problem is: I don't know what is the efficient way to realize it. Do I have to use Sphinx search engine?

Any idea?

Perhaps you could load a list of the first N users, and include a button to call an external script to serve up the next batch of users.

This is, of course, only if you are actually BROWSING, not searching.