Static content in a ram disk and haproxy+apache replicas grown as required. No CDN.

Even the most "dynamic" sites in terms on non user-specific content can be turned into a static snapshot via a simple cron job. That means the dynamic content is only ever hit by one person, that being cron.

Real user-specific dynamic content must require a login and cookies for haproxy to even let the connection pass the first stage of validation.