diff --git a/TODO.md b/TODO.md
deleted file mode 100644
index 9a319da2..00000000
--- a/TODO.md
+++ /dev/null
@@ -1,16 +0,0 @@
-# features/tweaks
-- emoji picker application
-- find a Masto/Pleroma app which works on mobile
-- remove hardcoded uid/gids outside of allocations.nix (used in impermanence code -- replace with username/groupname)
-
-
-# speed up cross compiling
-- <https://nixos.wiki/wiki/Cross_Compiling>
-- <https://nixos.wiki/wiki/NixOS_on_ARM>
-```nix
-   overlays = [{ ... }: {
-     nixpkgs.crossSystem.system = "aarch64-linux";
-   }];
-```
-- <https://github.com/nix-community/aarch64-build-box>
-	- apply for access to the community arm build box
diff --git a/modules/nixcache.nix b/modules/nixcache.nix
index 0ee143a1..2d801ad7 100644
--- a/modules/nixcache.nix
+++ b/modules/nixcache.nix
@@ -1,3 +1,13 @@
+# speed up builds from e.g. moby or lappy by having them query desko and servo first.
+# if one of these hosts is offline, instead manually specify just cachix:
+# - `nixos-rebuild --option substituters https://cache.nixos.org/`
+#
+# future improvements:
+# - apply for community arm build box:
+#   - <https://github.com/nix-community/aarch64-build-box>
+# - don't require all substituters to be online:
+#   - <https://github.com/NixOS/nix/pull/7188>
+
 { lib, config, ... }:
 
 with lib;