@jlrdw Thanks.
I too am developing at a very small scale, probably not even in distant comparison of such huge projects, but just got intrigued about what would be the factors driving mix of technologies.
I guess probably, such huge projects would be making their decision from collective wisdom of large number of tech experts they have at their disposal.
I have a dream of building an education portal someday, with lots of features for self paced learning on various topics - primarily school and college education with focus on progress made, reminder alerts and many such things which would make learning fun as well as self-encouraging. The main agenda is that I would like to ultimately make it free for all - all across the globe. Special focus to provide content in various languages especially for geographies with population consisting sizeable proportions of underprivileged or war/terrorism devastated fellow citizens of our world. Cause I believe that if kids and very young citizens have easy and free means for studying, they can develop themselves into good human beings and bring about a change in world order focused towards peace and development.
This kind of a project would be a significant effort much beyond the level at which I am working currently, but I guess I will have to start some where and then God willing I may be able to do at least something near to what I dream of.
Sorry for the digress, but every time I hear about how something was used in a huge project, I try to get some details thinking I might require something similar for the education portal. Thanks for your good wishes, wish you good luck too.