FastCGI will also solve the problem of having to create an expensive database connection per web request. It does that by reusing processes from one request to the next.

That problem will also be removed if you move the rest of the database interactions out of mod_perl. Heck, if you're right that virtually no database lookups happen then you could play the silly trick of replacing your database handle with a proxy object that will only connect if used. This will mean that any requests that don't touch the database don't connect to it.