Andreas Herrmann, the first Bazel community expert, talked about the value of a reproducible build of your software [media.ccc.de] and the merits of using an immutable distribution like Nix to make your builds better. Xe Iaso's talk on writing your own NixOS modules [media.ccc.de] for your own build dependencies to ensure your software is reproducable. Lots more talks, but mostly systemd-related: check out the list of talks [all-systems-go.io] and the recordings! [media.ccc.de]