>>11
There are various themes of "safety" in that system. For the case of the Haskell language, there's the safety of the language and also the safety of the language paradigm of being purely functional. For the case of Nix, there's the safety relating to the deployment of the binaries, system extensions, and system configuration being purely functional. Having a (reliably) reproducible system deployment is a very convenient way to reason the correctness of the system functions. This kind of correctness is useful everywhere but is also highly useful for the public facing service that is the web server.