I believe HN is written in PG's lisp like language called Arc. C, C++ and Java are the standard tools of the industry, so it's unusual and noteworthy when an a

I believe HN is written in PG's lisp like language called Arc. C, C++ and Java are the standard tools of the industry, so it's unusual and noteworthy when an alternative language or technology is used for a product. You can use a wide variety of languages for web development backends because it tends to be less sensitive to performance(the majority of hits should be hitting caches), it has simple IO requirements, and user sessions usually don't have much state so parallelism is easier. I'd argue that web development is much more about the product than technical programming challenges, so having the ability to iterate quickly is especially important and leads to favoring scripting languages over the traditional languages which are more suitable for complex and high performance software.