Well there are lots of different factors to this:
1. Amazon is using a custom built software with an highly optimized database
2. Their servers worth billions of dollars on a dedicated distributed network cluster
3. Their search engine probably uses different dedicated server networks with an optimized and indexed database with different layers of caching
And that's just 3 things. A wordpress powered website will never ever come even close to the speed of an amazon or imdb like search engine. For instants speed you will need a much better database architecture than wordpress, a much better specialized (non generic) cms built for your purposes and an insanely fast server.
I know people kind of expect that speed because they are used to it from google, amazon, imdb etc.., but it's not possible within the limits of a simple wordpress installation. It might be possible without it – with a custom build software (preferably not written in php) and with a better database engine. WordPress is a great solution to skip these steps as it provides a comfortable CMS system, but the speed is usually the price.Best,
If you like my products, don't forget to rate them on codecanyon :)