What software technology stack does Google+ use?

Given Google's history, it's more than likely largely proprietary and using C++, Java and maybe Python given those are the big 3 for them.  That said, Facebooks scaling problems aren't exactly well sourced.  People in the NoSQL movement insist upon it, but there's been no real indication from Facebook that they are really having issues or feel it's a problem.  Facebook does maintain a MySQL page, and regularly shares improvements and optimizations they have made.  Google does the same thing with Linux, and that's not exactly about being unable to scale.  I can't say they absolutely don't have an issue, but most of what's on the web is 2nd, 3rd and 4th hand accounts of rumors.  I wouldn't put much stock in it.  Facebook has the resources to move to something else.  Twitter did so with much less staff/resources.  If it was a problem, they would address it, they would be suffering from slow development and downtime.  Neither seem to be the case.  Facebooks last major outages were never attributed (or seemed to be) directly DB related.