ugh...I expected some beautiful girls, like in the "Making of the Pirelli Calendar", what a disappointment ;)

Philipp, I think they prototyped with PHP / MySQL, and then built the real one on the Google infrastructure.

Nothing by itself spectacular, but a lot of good processes highlighted there.

it was a great post but i didn't notice any information on how they came up with the code-name "CL2", it would be interesting to know how they come up with is.

Well whats wrong with the obvious, it was the second iteration of a CaLendar application?

Similarly LightHouse (aka Picasa Web Albums) has the id lh2.