Nix at SCALE

It is a very particular language trying to work a very particular problem space efficiently: It solves the problem of efficiently extracting your working solution out of a mostly broken and incompatible code base. And doing that reliably, repeatably and re-trace-ably. It also solves a very heavy communications problem on the side, which is communicating "your working solution" to others effectively so they can benefit from it.

I never actually used Nix (I read the Nix PhD thesis so I have a passing familiarity with the language), but my impression is that this is one area where Guix really shines: it uses Scheme for package and services definitions (well, for almost everything actually) instead of creating an ad-hoc language.

This becomes apparent in this article's section about module contracts. In Guix, the problem described in the article becomes a simpler problem of refactoring code to make the different services more composable. Perhaps even creating a function that accepts packages as parameters and returns a service definition that uses those packages in the service instead of the default ones.

Though admittedly it does have a high learning curve, especially if one isn't used to Lisp.