diff --git a/profiles/base/nix.nix b/profiles/base/nix.nix
index 5d7ce4f..77645f3 100644
--- a/profiles/base/nix.nix
+++ b/profiles/base/nix.nix
@@ -45,8 +45,10 @@
     max-silent-time = 3600; # kill long-running silent builds
 
     # === substitution
+    http-connections = 128; # default is 25
+    max-substitution-jobs = 128; # default is 16
     connect-timeout = 5; # timeout in seconds for binary caches
-    download-attempts = lib.mkDefault 2; # download attempts, in case a binary cache fails
+    download-attempts = 2; # download attempts, in case a binary cache fails
     # fallback = lib.mkDefault true; # fallback to building if a binary cache fails
 
     # === store