How does Google use Percolator, Dremel and Pregel?

Can you provide some insight into how Google uses Percolator, Dremel and Pregel?
Blind Five Year Old, SF, CA

Read more:

Have a question? Ask it in our Webmaster Help Forum:

Want your question to be answered on a video like this? Follow us on Twitter and look for an announcement when we take new questions:

More videos:
Webmaster Central Blog:
Webmaster Central: