Yieldex, a one-year-old company with a product for forecasting online ad inventory, is the winner of Amazon Web Services' startup challenge. The prize: $50,000 in cash, $50,000 in AWS credits, and a potential investment from Amazon.Yieldex's DynamicIQ service runs on Amazon's Elastic Compute Cloud and Simple Storage Service. DynamicIQ consists of analysis and planning tools and a "yield index" for online ad campaigns and ad placement.

Hundreds of startups competed in the contest, according to Amazon. Their applications were narrowed down to seven companies, which were invited to Amazon's headquarters to make pitches in front of a panel of judges from Amazon, followed by a second round of presentations to venture capitalists. The criteria for judging were originality of idea, market need, and implementation on AWS.

Yieldex CEO Tom Shields says the judges were "poker faced" during his company's presentation yesterday, so it was hard to tell how Yieldex would fare during the final round of judging. Shields gives a recap of the day-long proceedings on his Oxyfish blog.

Amazon VP Adam Selipsky cited Yieldex as an example of the kind of "dynamic new business" leveraging AWS. The six other finalists were Encoding.com, Knewton, MedCommons, Sonian, Pixily, and Zephyr. You can see video presentations from Yieldex and the other finalists here.