You can optionally use binary cache to skip building software and download it instead.
Edit /etc/nix/nix.conf (or related settings in NixOS config) and merge the new
values separated by spaces into the options:
substituters = ...https://plutonomicon.cachix.org https://cache.iog.io
trusted-public-keys = ... public-plutonomicon.cachix.org-1:3AKJMhCLn32gri1drGuaZmFrmnue+KkKrhhubQk/CWc= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=
Warning: do not add users to trusted-users because that gives them root accesswithout password.