If you are comparing non-Nix image build performance, Nix is comparable to BuildKit in that it’s able to parallelize a build graph and cache intermediary outputs. Nix doesn’t require a Dockerfile to build, and constructs the layers directly like in the article.

In terms of image size, since it’s dependencies are explicit (all the way down to glibc and lower), the Nix image is comparable to a scratch image with a single statically compiled binary.

Comparing to the existing Nix built images, we are moving image build performance from O(n) (n is number of Nix packages) to ~O(1) because the build process becomes just constructing a JSON referring to already built Nix packages.