diff --git a/src/Splitio/Services/Impressions/Classes/ImpressionsManager.cs b/src/Splitio/Services/Impressions/Classes/ImpressionsManager.cs
index c3195c5d..0385f66f 100644
--- a/src/Splitio/Services/Impressions/Classes/ImpressionsManager.cs
+++ b/src/Splitio/Services/Impressions/Classes/ImpressionsManager.cs
@@ -63,11 +63,9 @@ public KeyImpression Build(TreatmentResult result, Key key, Dictionary<string, o
             var impression = new KeyImpression(key.matchingKey, result.FeatureFlagName, result.Treatment, result.ImpTime, result.ChangeNumber, _labelsEnabled ? result.Label : null, key.bucketingKeyHadValue ? key.bucketingKey : null, result.ImpressionsDisabled);
 
             var validatorResult = _propertiesValidator.IsValid(properties);
-            if (validatorResult.Success)
+            if (validatorResult.Success && properties != null)
             {
-                if (properties != null) {
-                    impression.Properties = JsonConvert.SerializeObject(validatorResult.Value);
-                }
+                impression.Properties = JsonConvert.SerializeObject(validatorResult.Value);
             }
             
             try
diff --git a/src/Splitio/Services/Impressions/Classes/UniqueKeysTracker.cs b/src/Splitio/Services/Impressions/Classes/UniqueKeysTracker.cs
index 3b6c300c..6f9f6e1e 100644
--- a/src/Splitio/Services/Impressions/Classes/UniqueKeysTracker.cs
+++ b/src/Splitio/Services/Impressions/Classes/UniqueKeysTracker.cs
@@ -20,6 +20,7 @@ public class UniqueKeysTracker : TrackerComponent, IUniqueKeysTracker
         private readonly ConcurrentDictionary<string, HashSet<string>> _cache;
         private readonly IImpressionsSenderAdapter _senderAdapter;
         private readonly ISplitTask _cacheLongTermCleaningTask;
+        private int _keySize;
 
         public UniqueKeysTracker(ComponentConfig config,
             IFilterAdapter filterAdapter,
@@ -34,6 +35,7 @@ public UniqueKeysTracker(ComponentConfig config,
             _senderAdapter = senderAdapter;
             _cacheLongTermCleaningTask = cacheLongTermCleaningTask;
             _cacheLongTermCleaningTask.SetAction(_filterAdapter.Clear);
+            _keySize = 0;
         }
 
         #region Public Methods
@@ -48,8 +50,8 @@ public bool Track(string key, string featureName)
                 hashSet.Add(key);
                 return hashSet;
             });
-
-            if (_cache.Count >= _cacheMaxSize)
+            _keySize++;
+            if (_keySize >= _maxBulkSize)
             {
                 _taskBulkData.Start();
             }
@@ -76,8 +78,9 @@ protected override async Task SendBulkDataAsync()
             try
             {
                 var uniques = new ConcurrentDictionary<string, HashSet<string>>(_cache);
-
+                var keySize = _keySize;
                 _cache.Clear();
+                _keySize = 0;
 
                 if (!uniques.Any()) return;
 
@@ -85,23 +88,64 @@ protected override async Task SendBulkDataAsync()
                     .Select(v => new Mtks(v.Key, v.Value))
                     .ToList();
 
-                if (values.Count <= _maxBulkSize)
+                if (keySize <= _maxBulkSize)
                 {
                     await _senderAdapter.RecordUniqueKeysAsync(values);
                     return;
                 }
+                List<Mtks> bulksFlattened = FlattenBulks(values);
+                await SendAllBulks(bulksFlattened);
+            }
+            catch (Exception e)
+            {
+                _logger.Error("Exception caught sending Unique Keys.", e);
+            }
+        }
 
-                while (values.Count > 0)
+        protected async Task SendAllBulks(List<Mtks> bulksFlattened)
+        {
+            List<Mtks> bulksToSend = new List<Mtks>();
+            int bulkSize = 0;
+            foreach (var unique in bulksFlattened)
+            {
+                if ((unique.Keys.Count() + bulkSize) > _maxBulkSize)
                 {
-                    var bulkToPost = Util.Helper.TakeFromList(values, _maxBulkSize);
-
-                    await _senderAdapter.RecordUniqueKeysAsync(bulkToPost);
+                    await _senderAdapter.RecordUniqueKeysAsync(bulksToSend);
+                    bulkSize = 0;
+                    bulksToSend = new List<Mtks>();
                 }
+                bulkSize += unique.Keys.Count();
+                bulksToSend.Add(unique);
             }
-            catch (Exception e)
+            await _senderAdapter.RecordUniqueKeysAsync(bulksToSend);
+        }
+
+        protected List<Mtks> FlattenBulks(List<Mtks> values)
+        {
+            List<Mtks> bulksFlattened = new List<Mtks>();
+            foreach (var unique in values)
             {
-                _logger.Error("Exception caught sending Unique Keys.", e);
+                var bulks = ConvertToBulks(unique);
+                bulksFlattened.AddRange(bulks);
+            }
+            return bulksFlattened;
+        }
+
+        protected List<Mtks> ConvertToBulks(Mtks unique)
+        {
+            if (unique.Keys.Count > _maxBulkSize)
+            {
+                List<Mtks> chunks = new List<Mtks>();
+                var uniqueTemp = new List<String>(unique.Keys.ToArray());
+                var bulks = Util.Helper.ChunkBy(uniqueTemp, _maxBulkSize);
+                foreach (var bulk in bulks)
+                {
+                    chunks.Add(new Mtks(unique.Feature, new HashSet<string>(bulk)));
+                }
+                return chunks;
             }
+
+            return new List<Mtks> { unique };
         }
         #endregion
     }
diff --git a/src/Splitio/Services/Shared/Classes/ConfigService.cs b/src/Splitio/Services/Shared/Classes/ConfigService.cs
index 7ecb0eaa..6e9a684e 100644
--- a/src/Splitio/Services/Shared/Classes/ConfigService.cs
+++ b/src/Splitio/Services/Shared/Classes/ConfigService.cs
@@ -71,7 +71,7 @@ public BaseConfig ReadRedisConfig(ConfigurationOptions config)
             baseConfig.UniqueKeysRefreshRate = 300;
             baseConfig.ImpressionsCounterRefreshRate = 300;
             baseConfig.ImpressionsCountBulkSize = 10000;
-            baseConfig.UniqueKeysBulkSize = 10000;
+            baseConfig.UniqueKeysBulkSize = 5000;
 
             return baseConfig;
         }
@@ -93,7 +93,7 @@ public SelfRefreshingConfig ReadInMemoryConfig(ConfigurationOptions config)
                 ImpressionsCounterCacheMaxSize = baseConfig.ImpressionsCounterCacheMaxSize,
                 FlagSetsFilter = baseConfig.FlagSetsFilter,
                 FlagSetsInvalid = baseConfig.FlagSetsInvalid,
-                UniqueKeysBulkSize = 30000,
+                UniqueKeysBulkSize = 5000,
                 ImpressionsCountBulkSize = 30000,
                 UniqueKeysRefreshRate = 3600,
                 ImpressionsCounterRefreshRate = 1800, // Send bulk impressions count - Refresh rate: 30 min.
diff --git a/src/Splitio/Util/Helper.cs b/src/Splitio/Util/Helper.cs
index 1930434d..869967c8 100644
--- a/src/Splitio/Util/Helper.cs
+++ b/src/Splitio/Util/Helper.cs
@@ -3,6 +3,7 @@
 using Splitio.Telemetry.Domain.Enums;
 using Splitio.Telemetry.Storages;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Splitio.Util
 {
@@ -49,5 +50,14 @@ public static bool HasNonASCIICharacters(string input)
 
             return false;
         }
+
+        public static List<List<T>> ChunkBy<T>(List<T> source, int chunkSize)
+        {
+            return source
+                .Select((x, i) => new { Index = i, Value = x })
+                .GroupBy(x => x.Index / chunkSize)
+                .Select(x => x.Select(v => v.Value).ToList())
+                .ToList();
+        }
     }
 }
diff --git a/tests/Splitio-tests/Unit Tests/Impressions/UniqueKeysTrackerTests.cs b/tests/Splitio-tests/Unit Tests/Impressions/UniqueKeysTrackerTests.cs
index 419a616f..8df8e366 100644
--- a/tests/Splitio-tests/Unit Tests/Impressions/UniqueKeysTrackerTests.cs	
+++ b/tests/Splitio-tests/Unit Tests/Impressions/UniqueKeysTrackerTests.cs	
@@ -65,7 +65,7 @@ public async Task PeriodicTask_ShouldSendBulk()
         }
 
         [TestMethod]
-        public void Track_WithFullSize_ShouldSendBulk()
+        public void Track_WithFullSize_ShouldSendTwoBulk()
         {
             // Arrange.
             _cache.Clear();
@@ -101,16 +101,17 @@ public void Track_WithFullSize_ShouldSendBulk()
             Assert.AreEqual(1, values2.Count);
             _cache.TryGetValue("feature-name-test-3", out HashSet<string> values3);
             Assert.AreEqual(1, values3.Count);
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test", "feature-name-test-5"));
             Assert.IsTrue(_uniqueKeysTracker.Track("key-test-2", "feature-name-test-5"));
 
             Thread.Sleep(500);
-            _senderAdapter.Verify(mock => mock.RecordUniqueKeysAsync(It.IsAny<List<Mtks>>()), Times.Once);
+            _senderAdapter.Verify(mock => mock.RecordUniqueKeysAsync(It.IsAny<List<Mtks>>()), Times.Exactly(2));
 
             _cache.Clear();
         }
 
         [TestMethod]
-        public void Track_WithFullSize_ShouldSendTwoBulk()
+        public void Track_WithFullSize_ShouldSplitBulks()
         {
             // Arrange.
             _cache.Clear();
@@ -122,15 +123,21 @@ public void Track_WithFullSize_ShouldSendTwoBulk()
             _uniqueKeysTracker = new UniqueKeysTracker(config, _filterAdapter.Object, _cache, _senderAdapter.Object, task, cacheLongTermCleaningTask, sendBulkDataTask);
 
             // Act && Assert.
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-1", "feature-name-test"));
             Assert.IsTrue(_uniqueKeysTracker.Track("key-test-2", "feature-name-test"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-3", "feature-name-test"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-4", "feature-name-test"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-5", "feature-name-test"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-6", "feature-name-test"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-1", "feature-name-test-2"));
             Assert.IsTrue(_uniqueKeysTracker.Track("key-test-2", "feature-name-test-2"));
-            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-2", "feature-name-test-3"));
-            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-2", "feature-name-test-4"));
-            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-2", "feature-name-test-5"));
-            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-2", "feature-name-test-6"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-3", "feature-name-test-2"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-4", "feature-name-test-2"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-5", "feature-name-test-2"));
+            Assert.IsTrue(_uniqueKeysTracker.Track("key-test-6", "feature-name-test-2"));
 
             Thread.Sleep(500);
-            _senderAdapter.Verify(mock => mock.RecordUniqueKeysAsync(It.IsAny<List<Mtks>>()), Times.Exactly(2));
+            _senderAdapter.Verify(mock => mock.RecordUniqueKeysAsync(It.IsAny<List<Mtks>>()), Times.Exactly(4));
 
             _cache.Clear();
         }