diff --git a/pkgs/applications/virtualization/qemu/default.nix b/pkgs/applications/virtualization/qemu/default.nix
index d01af5dddb8..74c3f0e729d 100644
--- a/pkgs/applications/virtualization/qemu/default.nix
+++ b/pkgs/applications/virtualization/qemu/default.nix
@@ -297,6 +297,9 @@ stdenv.mkDerivation rec {
     qemu-system-i386 = "bin/qemu-system-i386";
   };
 
+  # Builds in ~3h with 2 cores, and ~20m with a big-parallel builder.
+  requiredSystemFeatures = [ "big-parallel" ];
+
   meta = with lib; {
     homepage = "http://www.qemu.org/";
     description = "A generic and open source machine emulator and virtualizer";
diff --git a/pkgs/development/libraries/aws-sdk-cpp/default.nix b/pkgs/development/libraries/aws-sdk-cpp/default.nix
index d6fbb97014d..7fd7b2fbbdd 100644
--- a/pkgs/development/libraries/aws-sdk-cpp/default.nix
+++ b/pkgs/development/libraries/aws-sdk-cpp/default.nix
@@ -63,6 +63,9 @@ stdenv.mkDerivation rec {
     ./cmake-dirs.patch
   ];
 
+  # Builds in 2+h with 2 cores, and ~10m with a big-parallel builder.
+  requiredSystemFeatures = [ "big-parallel" ];
+
   meta = with lib; {
     description = "A C++ interface for Amazon Web Services";
     homepage = "https://github.com/awslabs/aws-sdk-cpp";
diff --git a/pkgs/development/python-modules/pytorch/default.nix b/pkgs/development/python-modules/pytorch/default.nix
index 1436153e1db..59a8c74f709 100644
--- a/pkgs/development/python-modules/pytorch/default.nix
+++ b/pkgs/development/python-modules/pytorch/default.nix
@@ -297,6 +297,9 @@ in buildPythonPackage rec {
     install_name_tool -change @rpath/libc10.dylib $lib/lib/libc10.dylib $lib/lib/libshm.dylib
   '';
 
+  # Builds in 2+h with 2 cores, and ~15m with a big-parallel builder.
+  requiredSystemFeatures = [ "big-parallel" ];
+
   meta = with lib; {
     description = "Open source, prototype-to-production deep learning platform";
     homepage    = "https://pytorch.org/";
diff --git a/pkgs/servers/clickhouse/default.nix b/pkgs/servers/clickhouse/default.nix
index 063964b2f6a..02c0b4aa5e5 100644
--- a/pkgs/servers/clickhouse/default.nix
+++ b/pkgs/servers/clickhouse/default.nix
@@ -70,6 +70,9 @@ stdenv.mkDerivation rec {
 
   hardeningDisable = [ "format" ];
 
+  # Builds in 7+h with 2 cores, and ~20m with a big-parallel builder.
+  requiredSystemFeatures = [ "big-parallel" ];
+
   meta = with lib; {
     homepage = "https://clickhouse.tech/";
     description = "Column-oriented database management system";
diff --git a/pkgs/tools/filesystems/ceph/default.nix b/pkgs/tools/filesystems/ceph/default.nix
index 413fc9de185..57d5845c996 100644
--- a/pkgs/tools/filesystems/ceph/default.nix
+++ b/pkgs/tools/filesystems/ceph/default.nix
@@ -198,6 +198,9 @@ in rec {
 
     doCheck = false; # uses pip to install things from the internet
 
+    # Takes 7+h to build with 2 cores.
+    requiredSystemFeatures = [ "big-parallel" ];
+
     meta = getMeta "Distributed storage system";
 
     passthru.version = version;