Acquia Cloud Platform is a Drupal-tuned application lifecycle management suite with an infrastructure to support Drupal deployment workflow processes.
Drupal Multisite enables separate, independent sites to be served from a single codebase.
Drupal is a free and open-source web content management framework.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Varnish is a reverse caching proxy.