diff --git a/CentralHub.Api/Services/LocalizationService.cs b/CentralHub.Api/Services/LocalizationService.cs
index 7b257db..acd3463 100644
--- a/CentralHub.Api/Services/LocalizationService.cs
+++ b/CentralHub.Api/Services/LocalizationService.cs
@@ -3,6 +3,7 @@
 using CentralHub.Api.Dtos;
 using CentralHub.Api.Model;
 using CentralHub.Api.Model.Responses.Room;
+using CentralHub.Api.Threading;
 
 namespace CentralHub.Api.Services;
 
@@ -37,34 +38,39 @@ public async Task DoWorkAsync(CancellationToken stoppingToken)
     public async Task AggregateMeasurementsAsync(CancellationToken stoppingToken)
     {
         var roomMeasurementGroups = await _aggregatorRepository.GetRoomMeasurementGroupsAsync(stoppingToken);
-        var measuredRooms = new List<RoomDto>();
+        var allRooms = await _roomRepository.GetRoomsAsync(stoppingToken);
+        using var measuredRoomsMutex = new CancellableMutex<List<RoomDto>>(new List<RoomDto>());
 
-        foreach (var (roomId, measurementGroups) in roomMeasurementGroups)
+        await Parallel.ForEachAsync(
+            roomMeasurementGroups,
+            stoppingToken,
+            async (roomMeasurementGroup, stoppingToken) =>
         {
-            var room = await _roomRepository.GetRoomByIdAsync(
-                roomId,
-                stoppingToken);
+            var room = allRooms.SingleOrDefault(r => r.RoomDtoId == roomMeasurementGroup.Key);
 
             if (room == null)
             {
-                _logger.LogWarning("Room with id {RoomId} was not found.", roomId);
-                continue;
+                _logger.LogWarning("Room with id {RoomId} was not found.", roomMeasurementGroup.Key);
+                return;
             }
-            measuredRooms.Add(room);
+
+            await measuredRoomsMutex.Lock(m => m.Add(room), stoppingToken);
 
             await _aggregatorRepository.AddAggregatedMeasurementAsync(
-                CreateAggregatedMeasurement(room, measurementGroups),
+                CreateAggregatedMeasurement(room, roomMeasurementGroup.Value),
                 stoppingToken);
-        }
-
-        var allRooms = await _roomRepository.GetRoomsAsync(stoppingToken);
+        });
 
-        foreach (var room in allRooms.Where(r => !measuredRooms.Contains(r)))
+        await measuredRoomsMutex.Lock(async m =>
         {
-            await _aggregatorRepository.AddAggregatedMeasurementAsync(
-                CreateAggregatedMeasurement(room, new List<MeasurementGroup>()),
-                stoppingToken);
-        }
+            foreach (var room in allRooms.Where(r => !m.Contains(r)))
+            {
+                await _aggregatorRepository.AddAggregatedMeasurementAsync(
+                    CreateAggregatedMeasurement(room, new List<MeasurementGroup>()),
+                    stoppingToken);
+            }
+        },
+        stoppingToken);
     }
 
     private static AggregatedMeasurementDto CreateAggregatedMeasurement(RoomDto room, IReadOnlyCollection<MeasurementGroup> measurementGroups)