diff --git a/lib/charms/mongodb/v0/config_server_interface.py b/lib/charms/mongodb/v0/config_server_interface.py
index a0316ce33..58908bada 100644
--- a/lib/charms/mongodb/v0/config_server_interface.py
+++ b/lib/charms/mongodb/v0/config_server_interface.py
@@ -22,6 +22,7 @@
 KEY_FILE = "keyFile"
 HOSTS_KEY = "host"
 CONFIG_SERVER_DB_KEY = "config-server-db"
+MONGOS_SOCKET_URI_FMT = "%2Fvar%2Fsnap%2Fcharmed-mongodb%2Fcommon%2Fvar%2Fmongodb-27018.sock"
 
 # The unique Charmhub library identifier, never change it
 LIBID = "58ad1ccca4974932ba22b97781b9b2a0"
@@ -146,11 +147,10 @@ def _on_relation_changed(self, event) -> None:
         )
 
         # avoid restarting mongos when possible
-        if not updated_keyfile and not updated_config and self.charm.monogs_initialised:
+        if not updated_keyfile and not updated_config and self.is_mongos_running():
             return
 
         # mongos is not available until it is using new secrets
-        del self.charm.unit_peer_data["mongos_initialised"]
         logger.info("Restarting mongos with new secrets")
         self.charm.unit.status = MaintenanceStatus("starting mongos")
         self.charm.restart_mongos_service()
@@ -163,12 +163,11 @@ def _on_relation_changed(self, event) -> None:
             return
 
         # TODO: Follow up PR. Add a user for mongos once it has been started
-        self.charm.unit_peer_data["mongos_initialised"] = json.dumps(True)
         self.charm.unit.status = ActiveStatus()
 
     def is_mongos_running(self) -> bool:
         """Returns true if mongos service is running."""
-        with MongosConnection(None, "mongodb://localhost:27018") as mongo:
+        with MongosConnection(None, f"mongodb://{MONGOS_SOCKET_URI_FMT}") as mongo:
             return mongo.is_ready
 
     def update_config_server_db(self, config_server_db) -> bool:
diff --git a/lib/charms/mongodb/v1/helpers.py b/lib/charms/mongodb/v1/helpers.py
index 6140a7a11..96fe00970 100644
--- a/lib/charms/mongodb/v1/helpers.py
+++ b/lib/charms/mongodb/v1/helpers.py
@@ -90,15 +90,21 @@ def get_mongos_args(
     Returns:
         A string representing the arguments to be passed to mongos.
     """
+    # suborinate charm which provides its own config_server_db, should only use unix domain socket
+    binding_ips = (
+        f"--bind_ip {MONGODB_COMMON_DIR}/var/mongodb-27018.sock"
+        if config_server_db
+        else "--bind_ip_all"
+    )
+
     # mongos running on the config server communicates through localhost
-    # use constant for port
-    config_server_db = config_server_db or f"{config.replset}/localhost:27017"
+    config_server_db = config_server_db or f"{config.replset}/localhost:{Config.MONGODB_PORT}"
 
     full_conf_dir = f"{MONGODB_SNAP_DATA_DIR}{CONF_DIR}" if snap_install else CONF_DIR
     cmd = [
         # mongos on config server side should run on 0.0.0.0 so it can be accessed by other units
         # in the sharded cluster
-        "--bind_ip_all",
+        binding_ips,
         f"--configdb {config_server_db}",
         # config server is already using 27017
         f"--port {Config.MONGOS_PORT}",