diff --git a/example/flake.lock b/example/flake.lock
index ff90248f..c5955d9b 100644
--- a/example/flake.lock
+++ b/example/flake.lock
@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1687274257,
-        "narHash": "sha256-TutzPriQcZ8FghDhEolnHcYU2oHIG5XWF+/SUBNnAOE=",
+        "lastModified": 1693844670,
+        "narHash": "sha256-t69F2nBB8DNQUWHD809oJZJVE+23XBrth4QZuVd6IE0=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "2c9ecd1f0400076a4d6b2193ad468ff0a7e7fdc5",
+        "rev": "3c15feef7770eb5500a4b8792623e2d6f598c9c1",
         "type": "github"
       },
       "original": {
@@ -70,11 +70,11 @@
     },
     "process-compose-flake": {
       "locked": {
-        "lastModified": 1692810585,
-        "narHash": "sha256-Zc8nDSVkTUskB5mp9fh1mmOIUvx2pJ5V/Uq/0kxQ6B0=",
+        "lastModified": 1693927910,
+        "narHash": "sha256-qPKHnWWzHS2bAi/SsFePQkGFeC2E1jklUjEidfQwYLc=",
         "owner": "Platonic-Systems",
         "repo": "process-compose-flake",
-        "rev": "2a84a6c2c91c6244e5db8fd46551d5e7f31a85d3",
+        "rev": "5494afa0b6a7bc4ccf82ef1c36fe1fcdb4217255",
         "type": "github"
       },
       "original": {
@@ -95,11 +95,11 @@
     },
     "services-flake": {
       "locked": {
-        "lastModified": 1689713819,
-        "narHash": "sha256-ZjDQNRGpbxYSEYoqKmCdIOx+fV2q5lyiYWznHQ0fMkk=",
+        "lastModified": 1693467006,
+        "narHash": "sha256-negT+528qZyomG5ZotqNx7l0IA7vbJ2fGAM6F5ortAY=",
         "owner": "juspay",
         "repo": "services-flake",
-        "rev": "321ef32a28ed0e59160cf130c3a7c55e3b979e85",
+        "rev": "5fdd56f0900f05ef5bf1b8a348fabbd280f0c60b",
         "type": "github"
       },
       "original": {
diff --git a/nix/apache-kafka_test.nix b/nix/apache-kafka_test.nix
index 5f07fb2d..70dd7e92 100644
--- a/nix/apache-kafka_test.nix
+++ b/nix/apache-kafka_test.nix
@@ -1,10 +1,13 @@
 { pkgs, config, ... }: {
   services.zookeeper."z1".enable = true;
+  # To avoid conflicting with `zookeeper_test.nix` in case the tests are run in parallel
+  services.zookeeper."z1".port = 2182;
   services.apache-kafka."k1".enable = true;
+  services.apache-kafka."k1".zookeeper = "localhost:2182";
   settings.processes.test =
     {
       command = pkgs.writeShellApplication {
-        runtimeInputs = [ pkgs.bash config.package ];
+        runtimeInputs = [ pkgs.bash config.services.apache-kafka.k1.package ];
         text = ''
           bash kafka-topics.sh --list --bootstrap-server localhost:9092 
         '';
diff --git a/nix/elasticsearch.nix b/nix/elasticsearch.nix
index b808099b..1cdcd6ec 100644
--- a/nix/elasticsearch.nix
+++ b/nix/elasticsearch.nix
@@ -144,10 +144,10 @@ in
             startScript = pkgs.writeShellScript "es-startup" ''
               set -e
 
+              mkdir -m 0700 -p "${config.dataDir}"
               export ES_HOME=$(${pkgs.coreutils}/bin/realpath ${config.dataDir})
               export ES_JAVA_OPTS="${toString config.extraJavaOptions}"
               export ES_PATH_CONF="${config.dataDir}/config"
-              mkdir -m 0700 -p "${config.dataDir}"
               # Install plugins
               rm -f "${config.dataDir}/plugins"
               ln -sf ${esPlugins}/plugins "${config.dataDir}/plugins"
diff --git a/nix/postgres.nix b/nix/postgres.nix
index 39f6ada6..05a17d24 100644
--- a/nix/postgres.nix
+++ b/nix/postgres.nix
@@ -343,7 +343,8 @@ in
 
                 initdbArgs =
                   config.initdbArgs
-                  ++ (lib.optionals (config.superuser != null) [ "-U" config.superuser ]);
+                  ++ (lib.optionals (config.superuser != null) [ "-U" config.superuser ])
+                  ++ ["-D" config.dataDir ];
 
                 setupScript = pkgs.writeShellScriptBin "setup-postgres" ''
                   set -euo pipefail
@@ -351,6 +352,7 @@ in
 
                   if [[ ! -d "$PGDATA" ]]; then
                     set -x
+                    mkdir -p ${config.dataDir}
                     initdb ${lib.concatStringsSep " " initdbArgs}
                     set +x
 
diff --git a/nix/zookeeper.nix b/nix/zookeeper.nix
index f75dced8..4147c3d9 100644
--- a/nix/zookeeper.nix
+++ b/nix/zookeeper.nix
@@ -112,6 +112,7 @@ with lib;
                 ${config.extraConf}
                 ${config.servers}
                 admin.enableServer=false
+                4lw.commands.whitelist=stat
               '';
 
               configDir = pkgs.buildEnv {
@@ -136,8 +137,7 @@ with lib;
               command = "${startScript}/bin/start-zookeeper";
 
               readiness_probe = {
-                # TODO: need to find a better way to check if zookeeper is ready, maybe `zkCli.sh`?
-                exec.command = "${pkgs.netcat.nc}/bin/nc -z localhost ${toString config.port}";
+                exec.command = "echo stat | ${pkgs.netcat.nc}/bin/nc localhost ${toString config.port}";
                 initial_delay_seconds = 2;
                 period_seconds = 10;
                 timeout_seconds = 4;
diff --git a/nix/zookeeper_test.nix b/nix/zookeeper_test.nix
index 22e9b825..848ac9cb 100644
--- a/nix/zookeeper_test.nix
+++ b/nix/zookeeper_test.nix
@@ -3,9 +3,9 @@
   settings.processes.test =
     {
       command = pkgs.writeShellApplication {
-        runtimeInputs = [ pkgs.bash config.package ];
+        runtimeInputs = [ config.services.zookeeper.z1.package pkgs.netcat.nc ];
         text = ''
-          bash zkCli.sh -server localhost:2181 get /
+          echo stat | nc localhost 2181
         '';
         name = "zookeeper-test";
       };
diff --git a/test/flake.lock b/test/flake.lock
index ae98ebc2..e4467793 100644
--- a/test/flake.lock
+++ b/test/flake.lock
@@ -54,11 +54,11 @@
     },
     "process-compose-flake": {
       "locked": {
-        "lastModified": 1692810585,
-        "narHash": "sha256-Zc8nDSVkTUskB5mp9fh1mmOIUvx2pJ5V/Uq/0kxQ6B0=",
+        "lastModified": 1693927910,
+        "narHash": "sha256-qPKHnWWzHS2bAi/SsFePQkGFeC2E1jklUjEidfQwYLc=",
         "owner": "Platonic-Systems",
         "repo": "process-compose-flake",
-        "rev": "2a84a6c2c91c6244e5db8fd46551d5e7f31a85d3",
+        "rev": "5494afa0b6a7bc4ccf82ef1c36fe1fcdb4217255",
         "type": "github"
       },
       "original": {