Drupal is optimized for use on Amazon Web Service servers!
Amazon Web Service is a reliable and highly functional cloud computing platform, and it is used by many enterprise corporations. It is also possible to use Paas (cloud).
Amazon Web Service Features
Amazon Web Service Security
Details on Amazon Web Service's security can be found here.
It is possible to use Drupal's Paas (Cloud) on AWS!
Digital Circus, using the Acquia Network provided by Acquia, makes it possible to present high-functioning Drupal entry and maintenance service to the Japanese CMS market. The Acquia Network uses the Acquia Cloud together with performance-enhancing tools, analysis tools, and other monitoring services.
Digital Circus partnered with Acquia to provide Drupal development, operational monitoring, and Japanese-language support for the Japanese market.
The CTO of Acquia is Drupal founder Dries Buytaert, and they provide a Drupal platform service called Acquia Cloud. Many global corporations use the Acquia service and their reputation is very strong. Many of the companies are ranked in the top 500 high-growth US companies.