A comment in Why did Facebook decide to shut down Parse? on Hacker News:
I started my career with the belief that your company has one tech stack, the chief architect chooses it when the company is founded, and that you never ever rewrite it because you're in for a world of pain if you do.
I learned that basically no company that experiences hyper-growth ever does this. Instead, the founder chooses a tech stack based on whatever he knows best and will let him write a v1 quickest - whether it be Java (Google), Perl (EBay), PHP (Facebook), or Common Lisp (Reddit). The first few employees collectively say that the founder is an idiot, choose a different tech stack (usually whatever's hot right now - probably Go or Node.js at this time, Python or Rails in 2005), and rewrite the whole product. They hire an experienced VP who says that the first few employees are idiots, chooses a different tech stack (often the tried and true enterprise favorites of C++ or Java), and dictates that everyone rewrite the product. Eventually, managers with more recent experience in that language get hired, who collectively say that that VP was an idiot, and the real way to do C++/Java is with Guice, Boost, C++11, etc, and rewrite the product that way. Development grinds to a halt, and the company buys a bunch of hot startups who wrote in whatever language they were familiar with, who are technical idiots but managed to build a product that everyone likes.