diff --git a/sync/models/base.py b/sync/models/base.py
index 0e6e857..13b50b7 100644
--- a/sync/models/base.py
+++ b/sync/models/base.py
@@ -11,10 +11,6 @@ class BaseModel(models.Model):
     class Meta:
         abstract = True
 
-    def get_parent_reference(self):
-        """Return a tuple: model_name, model_id"""
-        return None, None
-
     def get_children_by_model(self):
         """
         Returns a dictionary where:
@@ -124,18 +120,6 @@ class BaseModel(models.Model):
 
         return instances
 
-    # def related_instances(self):
-    #     instances = []
-    #     children_by_model = self.get_children_by_model()
-    #     all_children = [item for sublist in children_by_model.values() for item in sublist]
-    #     instances.extend(all_children)
-
-    #     parents_by_model = self.get_parents_by_model()
-    #     instances.extend(parents_by_model.values())
-
-    #     return instances
-
-
 class SideStoreModel(BaseModel):
     store_id = models.CharField(max_length=100)
 
diff --git a/sync/signals.py b/sync/signals.py
index 33eaeda..d1771cd 100644
--- a/sync/signals.py
+++ b/sync/signals.py
@@ -5,13 +5,7 @@ from .models import DataAccess, ModelLog, ModelOperation, BaseModel, SideStoreMo
 from django.contrib.auth import get_user_model
 from django.utils import timezone
 
-from channels.layers import get_channel_layer
-from asgiref.sync import async_to_sync
-
-from threading import Timer
-# from functools import partial
-
-# Synchronization
+from .ws_sender import websocket_sender
 
 User = get_user_model()
 
@@ -19,7 +13,7 @@ User = get_user_model()
 def synchronization_prepare(sender, instance, created=False, **kwargs):
 
     # some classes are excluded in settings_app.py: SYNC_APPS
-    if not isinstance(instance, BaseModel):
+    if not isinstance(instance, BaseModel) and not isinstance(instance, User):
         return
 
     save_model_log_if_possible(instance, kwargs.get('signal'), created)
@@ -57,10 +51,15 @@ def notify_impacted_users(instance, signal):
 
     print(f'notify: {user_ids}')
     for user_id in user_ids:
-        send_user_message(user_id)
+        websocket_sender.send_user_message(user_id)
+        # send_user_message(user_id)
 
 def save_model_log_if_possible(instance, signal, created):
-    user = instance.last_updated_by
+    if isinstance(instance, User):
+        user = instance
+    else:
+        user = instance.last_updated_by
+
     if user:
         if signal == post_save or signal == pre_save:
             if created:
@@ -79,10 +78,11 @@ def save_model_log_if_possible(instance, signal, created):
             ModelLog.objects.filter(model_id=instance.id).delete()
 
         users = {user}
-        data_access_list = related_data_access(instance)
-        for data_access in data_access_list:
-            users.add(data_access.owner)
-            users.update(data_access.shared_with.all())
+        if isinstance(instance, BaseModel):
+            data_access_list = related_data_access(instance)
+            for data_access in data_access_list:
+                users.add(data_access.owner)
+                users.update(data_access.shared_with.all())
         if isinstance(instance, DataAccess):
             users.add(instance.owner)
             users.update(instance.shared_with.all())
@@ -102,7 +102,7 @@ def save_model_log(users, model_operation, model_name, model_id, store_id):
     if existing_log:
         # print(f'update existing log {existing_log.users} ')
         existing_log.date = now
-        existing_log.model_operation = model_operation
+        # existing_log.operation = model_operation
         existing_log.save()
         existing_log.users.set(users)
     else:
@@ -135,32 +135,33 @@ def handle_shared_with_changes(sender, instance, action, pk_set, **kwargs):
         instance.create_access_log(users, 'REVOKE_ACCESS')
 
     for user_id in pk_set:
-        send_user_message(user_id)
+        websocket_sender.send_user_message(user_id)
+        # send_user_message(user_id)
 
-def send_user_message(user_id):
+# def send_user_message(user_id):
 
-    if not hasattr(send_user_message, '_buffer'):
-        send_user_message._buffer = set()
-        send_user_message._timer = None
+#     if not hasattr(send_user_message, '_buffer'):
+#         send_user_message._buffer = set()
+#         send_user_message._timer = None
 
-    send_user_message._buffer.add(user_id)
+#     send_user_message._buffer.add(user_id)
 
-    if send_user_message._timer:
-        send_user_message._timer.cancel()
+#     if send_user_message._timer:
+#         send_user_message._timer.cancel()
 
-    def send_buffered_messages():
-        channel_layer = get_channel_layer()
-        for buffered_id in send_user_message._buffer:
-            group_name = f"sync_{buffered_id}"
-            print(f">>> send to group {group_name}")
-            async_to_sync(channel_layer.group_send)(
-                group_name, {"type": "sync.update", "message": "hello"}
-            )
-        send_user_message._buffer.clear()
-        send_user_message._timer = None
+#     def send_buffered_messages():
+#         channel_layer = get_channel_layer()
+#         for buffered_id in send_user_message._buffer:
+#             group_name = f"sync_{buffered_id}"
+#             print(f">>> send to group {group_name}")
+#             async_to_sync(channel_layer.group_send)(
+#                 group_name, {"type": "sync.update", "message": "hello"}
+#             )
+#         send_user_message._buffer.clear()
+#         send_user_message._timer = None
 
-    send_user_message._timer = Timer(0.1, send_buffered_messages)
-    send_user_message._timer.start()
+#     send_user_message._timer = Timer(0.1, send_buffered_messages)
+#     send_user_message._timer.start()
 
 @receiver(pre_delete, sender=DataAccess)
 def revoke_access_after_delete(sender, instance, **kwargs):
diff --git a/sync/views.py b/sync/views.py
index 40db54a..affe711 100644
--- a/sync/views.py
+++ b/sync/views.py
@@ -108,7 +108,7 @@ class SynchronizationApi(HierarchyApiView):
             serializer = serializer_class(instance, data=data, context={'request': request})
             if serializer.is_valid():
                 if instance.last_update <= serializer.validated_data.get('last_update'):
-                    print('>>> update')
+                    # print('>>> update')
                     serializer.save()
                     return Response(serializer.data, status=status.HTTP_200_OK)
                 else:
diff --git a/sync/ws_sender.py b/sync/ws_sender.py
new file mode 100644
index 0000000..b22da39
--- /dev/null
+++ b/sync/ws_sender.py
@@ -0,0 +1,46 @@
+from channels.layers import get_channel_layer
+from asgiref.sync import async_to_sync
+from threading import Timer
+
+class WebSocketSender:
+    """
+    Manages WebSocket notifications for users with individual buffering timers.
+    """
+    def __init__(self):
+        self._user_timers = {}   # Dictionary to store user-specific timers
+        self._buffer_timeout = 0.1  # Debounce timeout in seconds
+
+    def send_user_message(self, user_id):
+        """
+        Schedules a notification for a specific user with debouncing.
+        """
+        # Cancel existing timer for this user if any
+        if user_id in self._user_timers and self._user_timers[user_id]:
+            self._user_timers[user_id].cancel()
+
+        # Create new timer for this user
+        self._user_timers[user_id] = Timer(
+            self._buffer_timeout,
+            self._send_message,
+            args=[user_id]
+        )
+        self._user_timers[user_id].start()
+
+    def _send_message(self, user_id):
+        """
+        Sends the WebSocket message for a specific user.
+        """
+        channel_layer = get_channel_layer()
+        group_name = f"sync_{user_id}"
+        print(f">>> send to group {group_name}")
+
+        async_to_sync(channel_layer.group_send)(
+            group_name,
+            {"type": "sync.update", "message": "hello"}
+        )
+
+        # Cleanup timer reference
+        self._user_timers[user_id] = None
+
+# Create a singleton instance
+websocket_sender = WebSocketSender()
diff --git a/tournaments/models/custom_user.py b/tournaments/models/custom_user.py
index 383b058..8c25ebb 100644
--- a/tournaments/models/custom_user.py
+++ b/tournaments/models/custom_user.py
@@ -48,9 +48,6 @@ class CustomUser(AbstractUser):
             'summons_use_full_custom_message', 'match_formats_default_duration', 'bracket_match_format_preference',
             'group_stage_match_format_preference', 'loser_bracket_match_format_preference', 'device_id']
 
-    def get_parent_reference(self):
-        """Override in child models to provide parent reference"""
-        return None, None
 
     def __str__(self):
         return self.username
diff --git a/tournaments/models/date_interval.py b/tournaments/models/date_interval.py
index 56d4696..6593812 100644
--- a/tournaments/models/date_interval.py
+++ b/tournaments/models/date_interval.py
@@ -8,7 +8,3 @@ class DateInterval(BaseModel):
     court_index = models.IntegerField()
     start_date = models.DateTimeField()
     end_date = models.DateTimeField()
-
-    # Data Access
-    def get_parent_reference(self):
-        return 'Event', self.event.id
diff --git a/tournaments/models/group_stage.py b/tournaments/models/group_stage.py
index fa89df0..41d2831 100644
--- a/tournaments/models/group_stage.py
+++ b/tournaments/models/group_stage.py
@@ -15,9 +15,6 @@ class GroupStage(SideStoreModel):
     start_date = models.DateTimeField(null=True, blank=True)
     name = models.CharField(max_length=200, null=True, blank=True)
 
-    # Data Access
-    def get_parent_reference(self):
-        return 'Event', self.tournament.event.id
 
     def __str__(self):
         return self.display_name()
diff --git a/tournaments/models/match.py b/tournaments/models/match.py
index 23bd996..779d303 100644
--- a/tournaments/models/match.py
+++ b/tournaments/models/match.py
@@ -26,10 +26,6 @@ class Match(SideStoreModel):
     court_index = models.IntegerField(null=True, blank=True)
     confirmed = models.BooleanField(default=False)
 
-    # Data Access
-    def get_parent_reference(self):
-        return 'Event', self.tournament().event.id
-
     def __str__(self):
         names = " / ".join(self.player_names())
         return f"{self.stage_name()} #{self.index}: {names}"
diff --git a/tournaments/models/player_registration.py b/tournaments/models/player_registration.py
index e087425..668f507 100644
--- a/tournaments/models/player_registration.py
+++ b/tournaments/models/player_registration.py
@@ -34,10 +34,6 @@ class PlayerRegistration(SideStoreModel):
     source = models.IntegerField(choices=PlayerDataSource.choices, null=True, blank=True)
     has_arrived = models.BooleanField(default=False)
 
-    # Data Access
-    def get_parent_reference(self):
-        return 'Event', self.team_registration.tournament.event.id
-
     def __str__(self):
         return self.name()
 
diff --git a/tournaments/models/round.py b/tournaments/models/round.py
index c94582b..33b1ae7 100644
--- a/tournaments/models/round.py
+++ b/tournaments/models/round.py
@@ -10,10 +10,6 @@ class Round(SideStoreModel):
     format = models.IntegerField(default=FederalMatchCategory.NINE_GAMES, choices=FederalMatchCategory.choices, null=True, blank=True)
     start_date = models.DateTimeField(null=True, blank=True)
 
-    # Data Access
-    def get_parent_reference(self):
-        return 'Event', self.tournament.event.id
-
     def __str__(self):
         if self.parent:
             return f"LB: {self.name()}"
diff --git a/tournaments/models/team_registration.py b/tournaments/models/team_registration.py
index 44a56cb..48f3939 100644
--- a/tournaments/models/team_registration.py
+++ b/tournaments/models/team_registration.py
@@ -30,10 +30,6 @@ class TeamRegistration(SideStoreModel):
     final_ranking = models.IntegerField(null=True, blank=True)
     points_earned = models.IntegerField(null=True, blank=True)
 
-    # Data Access
-    def get_parent_reference(self):
-            return 'Event', self.tournament.event.id
-
     def __str__(self):
         if self.name:
             return self.name
diff --git a/tournaments/models/team_score.py b/tournaments/models/team_score.py
index 49d3a69..b032554 100644
--- a/tournaments/models/team_score.py
+++ b/tournaments/models/team_score.py
@@ -13,10 +13,6 @@ class TeamScore(SideStoreModel):
     def __str__(self):
         return f"{self.match.stage_name()} #{self.match.index}: {self.player_names()}"
 
-    # Data Access
-    def get_parent_reference(self):
-        return 'Event', self.tournament().event.id
-
     def tournament(self):
         if self.team_registration:
             return self.team_registration.tournament
diff --git a/tournaments/models/tournament.py b/tournaments/models/tournament.py
index 929dd26..2df614d 100644
--- a/tournaments/models/tournament.py
+++ b/tournaments/models/tournament.py
@@ -60,10 +60,6 @@ class Tournament(BaseModel):
     hide_points_earned = models.BooleanField(default=False)
     publish_rankings = models.BooleanField(default=False)
 
-    # Data Access
-    def get_parent_reference(self):
-        return 'Event', self.event.id
-
     def get_child_models(self):
         return {
             'Round': 'round_set',