system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does Google search such massive amounts of data and return results in less than a second?

I get they are probably doing some optimized caching and their algorithm is proprietary but at a high level, how does Google work with such good performance numbers?
gpt
>I get they are probably doing some optimized caching and their algorithm is proprietary but at a high level, how does Google work with such good performance numbers?  
  
They do not perform live-searches on websites. They search their own **index** which is basically a collection of cross-referenced dictionaries compiled from all the internet's content they ever crawled. In a sense they have everything *pre*-searched.