Like other things at Google, artificial intelligence and computer automation perform some of the grunt work.
This article is interesting. My own impression, Google is more dynamic than I thought. They use free software like Linux, and even modify the Linux kernel. They make their own programming language and even thought of making their own data chip. Their engineers study chips in detail, that means that the know everything about clock cycles, risc processors, registers, input / output, etc.
KW's: Intelligence, adaptivity and a decentralized and dynamic cost effective business model.