As others have indicated, it&#x27;s a proxy server rather than a general purpose webserver. There&#x27;s no code relation between the two servers; it&#x27;s simply that the team at Yahoo chose to pursue it as an Apache Foundation project when they open sourced it.<p>ATS scales orders of magnitude better than Apache, due to its process model. Whereas at Yahoo we would budget between 30-200 simultaneous connections per Apache server (prefork), the proxy service which I ran using ATS was budgeted for over 100,000 concurrent connections per machine.<p>It&#x27;s significantly less featureful than Apache, but it does caching substantially better than any other cache server commonly available (nginx, apache, squid, varnish).