Application uptime in the cloud should be addressed by the developer as much as infrastructure uptime is addressed by the cloud provider. And many cloud customers get it, according to Werner Vogels, CTO at Amazon.com.

Amazon Web Services has been pushing its cloud customers to build applications across multiple of its "availability zones" for fault tolerance for quite some time now. The company started driving the point more aggressively after a major outage recently took down many websites, including some high-profile ones, like Reddit.com, Quora.com, GroupMe.com and Foursquare.

In a "post-mortem" it released following the three-day-long incident in April, Amazon said it was going to increase focus on making it easier for customers to build applications across multiple availability zones to prevent complete service outages in cases of single-site failures.

"In this event, some customers were seriously impacted, and yet others had resources that were impacted but saw nearly no impact on their applications," the AWS post-mortem statement read.

In his keynote at this week’s Structure conference in San Francisco, Vogels said users were getting smarter about building applications deployed in the cloud to be more fault tolerant. "Young businesses as well as enterprises are building increasingly sophisticated applications in the cloud," he said.

One such company is Advanced Innovations, which deployed its applications in the Amazon cloud’s availability zones on the US east coast and in Europe. "If ever the complete east coast of the US would disappear from the map, their customers can still be served out of the EU region," Vogels said about Advanced Innovations’ architecture.

Advanced Innovations designs and operates global supply-chain networks for design, manufacturing and delivery of electronic products.

Another organization Vogels used as an example of a sophisticated AWS user was the US government with its Recovery.gov website, which runs entirely on top of the Amazon cloud. "Recovery.gov is not just a simple website," he said. "It’s actually built out of highly-highly complex components."

Finally Amazon itself is a huge AWS customer. The company’s online retail outlet Amazon.com has been served out of AWS 100% since November 2010.

Vogels continued the tradition of updating the audience at the annual Structure event on growth of the AWS infrastructure. The number of objects stored in the Amazon cloud today is approaching 350bn objects. For comparison, the company was storing between 100bn and 120bn objects in the first quarter of 2010.

The company’s priorities for 2011 include adding more geographies to its global data center footprint, making it easier to build and manage applications on AWS, releasing new database offerings and broadening its support offerings.