Wow, this was eye-opening! 80,000 builds and 50% of the Google code base changes each month! At this scale, their HEAD development (as described in the above link) and their discipline and detail in unit testing & code reviews is incredible…

Also, their approach to bug prediction is a very interesting. Basically they, devised an algorithm that predicts which source files are due to have a bug introduced based on various metrics. This algorithm then pops up a note in their code review tool so that the review can be handed off to a more experienced reviewer.