Slashdot may seem complex to the user, but the all the database backend has to do is fetch records by date, or by subject.
By complex I mean queries of more than 20 lines of SQL, JOINs over six tables, aggregates.
MySQL is very good for simple selects that get a few records at a time.
Give it something more complex and it chokes.
I recommend PostgreSQL. That's also free, but it is much more advanced than MySQL. It has row-level-locking, stored procedures, a Write ahead log, subqueries and supports the full ANSI SQL standard.
