diff --git a/.forgejo/workflows/check.yml b/.forgejo/workflows/check.yml
index 3479450..b693b74 100644
--- a/.forgejo/workflows/check.yml
+++ b/.forgejo/workflows/check.yml
@@ -27,11 +27,6 @@ jobs:
               build --out-link /var/lib/gitea-runner/tankstelle/.local/state/nix/results/"$target" ".#nixosConfigurations.${target}.config.system.build.toplevel"
           done
 
-          for check in $(nix flake show --json --all-systems | jq --raw-output '
-            .checks."x86_64-linux" |
-            to_entries[] |
-            .key'
-          ); do
-            nix --print-build-logs --verbose --accept-flake-config --access-tokens '' \
-              build --out-link /var/lib/gitea-runner/tankstelle/.local/state/nix/results/"$check" ".#checks.x86_64-linux.${check}"
-          done
+          sed -i 's/virtualisation.cores .*/virtualisation.cores = 16;/' tests/keycloak.nix
+          sed -i 's/virtualisation.memorySize .*/virtualisation.memorySize = 16384;/' tests/keycloak.nix
+          nix --accept-flake-config --access-tokens '' develop --command nix-fast-build --no-nom --skip-cached --systems "aarch64-linux x86_64-linux" --max-jobs 6
diff --git a/flake.nix b/flake.nix
index 496599e..fe6e32e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -99,7 +99,7 @@
           devShells.default = pkgs.mkShell {
             buildInputs = with pkgs; [
               deploy-rs
-              nixpkgs-fmt
+              nix-fast-build
               agenix
               age-plugin-yubikey
               cachix
diff --git a/tests/keycloak.nix b/tests/keycloak.nix
index 9f5241b..0d4a825 100644
--- a/tests/keycloak.nix
+++ b/tests/keycloak.nix
@@ -46,6 +46,7 @@ in
 
       systemd.tmpfiles.rules = [ "f /tmp/dbf 1777 root root 10d password" ];
 
+      virtualisation.cores = 1;
       virtualisation.memorySize = 4096;
 
       pub-solar-os.auth = {
diff --git a/tests/website.nix b/tests/website.nix
index 6d4f46d..db3a0aa 100644
--- a/tests/website.nix
+++ b/tests/website.nix
@@ -31,6 +31,7 @@
         ./support/global.nix
       ];
 
+      virtualisation.cores = 1;
       virtualisation.memorySize = 4096;
 
       networking.interfaces.eth0.ipv4.addresses = [