garbas: I'm dropping this knowledge here before it leaves my brain. I hope to come back and put it in some sort of nicer form.

• Purpose of releases.nixos.org is store all release artifects
• Acts as immutable storage (in contrast to channels.nixos.org which acts as mutable storage)
• S3 bucket is called nix-releases and at the time of writing is configured here: https://github.com/NixOS/nixos-org-configurations/blob/master/terraform/releases.tf
• This service is used by channels.nixos.org that creates redirects for latest successful channels build