>For that matter, you can get the same effect with the MySQL prompt and a sh...

nostrademons · on March 12, 2008

  EXPLAIN SELECT username FROM users WHERE username = $dc_user

Then look at the output, and either

  CREATE INDEX users_username ON users(username)

Or cache the result, or do something else to fix the performance problem...

If you meant "How do you find out it was in the registration check?", that's what the slow query log and query profilers are for...