- Microsoft has lost one of the key architects of its data-center strategy, James Hamilton, to rival Amazon Web Services.

Hamilton, a former data-center futures architect at Microsoft, has left the company to become a vice president distinguished engineer at AWS, the company confirmed in an e-mail.

The company did not say specifically what Hamilton's role will be, saying only that he will "start putting his expertise" to work in "designing and deploying systems that are secure and that scale reliably and cost-effectively" at AWS beginning in January.

Hamilton disclosed that he had left Microsoft on his Microsoft home page. While at Microsoft, he was instrumental in designing the company's current and expanding data-center strategy as part of the data-center futures team, which is responsible for data-center efficiency, speed of deployment and reliability.

Hamilton also blogged about his impending move on his Perspectives blog, saying that he has had a "super-interesting time at Microsoft" and that leaving the company is "tough."

Microsoft did not immediately return requests for comment Monday on Hamilton's departure.

Prior to joining the data-center futures team, Hamilton was an architect on the Live Platform Services team. Before that he was general manager for Microsoft Exchange Hosted Services and also worked in the SQL Server database group.

Microsoft has been building out its data-center strategy for the last few years, adding new data centers around the U.S. and overseas, to support its burgeoning software-as-a-service and cloud-computing strategies. This year the company put a significant amount of investment into its Live search engine and Windows Live set of services, among other offerings, specifically to compete with AWS and also Google.

In October Microsoft revealed one of its most significant offerings to date to advance its cloud-computing strategy, the Windows Azure Services Platform. This application-development platform and infrastructure is entirely hosted in Microsoft's data centers.

In the meantime, AWS, Amazon.com's pioneering cloud-computing subsidiary, continues to expand its own footprint. Last week, the company revealed its first pay-as-you-go application- and service-delivery in Europe.