Can't speak to AWS, but I know that the e-commerce side of Amazon.com is A/B tested to within an inch of its life. They test absolutely everything, including colors, size, layout, spacing, etc to check for the best conversion rate. They have a huge team of developers and designers working just on this site optimization and they're constantly running experiments.
It may not be good UX as measured by some aesthetic standard or set of best practices, but the site is accomplishing its goal for Amazon and arguably the consumers who use it.
It may not be good UX as measured by some aesthetic standard or set of best practices, but the site is accomplishing its goal for Amazon and arguably the consumers who use it.