diff --git a/Framework/OverwatchTranscript/BucketSet.cs b/Framework/OverwatchTranscript/BucketSet.cs
new file mode 100644
index 00000000..544dc5b7
--- /dev/null
+++ b/Framework/OverwatchTranscript/BucketSet.cs
@@ -0,0 +1,111 @@
+namespace OverwatchTranscript
+{
+    public class BucketSet
+    {
+        private const int numberOfActiveBuckets = 5;
+        private readonly object _counterLock = new object();
+        private int pendingAdds = 0;
+
+        private readonly object _bucketLock = new object();
+        private readonly List<EventBucket> fullBuckets = new List<EventBucket>();
+        private readonly List<EventBucket> activeBuckets = new List<EventBucket>();
+        private int activeBucketIndex = 0;
+        private bool closed = false;
+        private readonly string workingDir;
+
+        public BucketSet(string workingDir)
+        {
+            this.workingDir = workingDir;
+
+            for (var i = 0; i < numberOfActiveBuckets;i++)
+            {
+                AddNewBucket();
+            }
+        }
+
+        public string Error { get; private set; } = string.Empty;
+
+        public void Add(DateTime utc, object payload)
+        {
+            if (closed) throw new Exception("Buckets already closed!");
+            AddPending();
+            Task.Run(() => AddInternal(utc, payload));
+        }
+
+        public bool IsEmpty()
+        {
+            return fullBuckets.All(b => b.Count == 0) && activeBuckets.All(b => b.Count == 0);
+        }
+
+        public IFinalizedBucket[] FinalizeBuckets()
+        {
+            closed = true;
+            WaitForZeroPending();
+
+            var buckets = fullBuckets.Concat(activeBuckets).ToArray();
+            return buckets.Select(b => b.FinalizeBucket()).ToArray();
+        }
+
+        private void AddInternal(DateTime utc, object payload)
+        {
+            try
+            {
+                lock (_bucketLock)
+                {
+                    var current = activeBuckets[activeBucketIndex];
+                    current.Add(utc, payload);
+                    activeBucketIndex = (activeBucketIndex + 1) % numberOfActiveBuckets;
+
+                    if (current.IsFull)
+                    {
+                        fullBuckets.Add(current);
+                        activeBuckets.Remove(current);
+                        AddNewBucket();
+                    }
+                    RemovePending();
+                }
+            }
+            catch (Exception ex)
+            {
+                Error += ex.ToString();
+            }
+        }
+
+        private void AddNewBucket()
+        {
+            lock (_bucketLock)
+            {
+                activeBuckets.Add(new EventBucket(Path.Combine(workingDir, Guid.NewGuid().ToString())));
+            }
+        }
+
+        private void AddPending()
+        {
+            lock (_counterLock)
+            {
+                pendingAdds++;
+            }
+        }
+
+        private void RemovePending()
+        {
+            lock (_counterLock)
+            {
+                pendingAdds--;
+                if (pendingAdds < 0) Error += "Pending less than zero";
+            }
+        }
+
+        private void WaitForZeroPending()
+        {
+            while (true)
+            {
+                lock (_counterLock)
+                {
+                    if (pendingAdds == 0) return;
+                }
+                Thread.Sleep(10);
+            }
+        }
+    }
+}
diff --git a/Framework/OverwatchTranscript/EventBucket.cs b/Framework/OverwatchTranscript/EventBucket.cs
index 09ee121c..a71fa4b9 100644
--- a/Framework/OverwatchTranscript/EventBucket.cs
+++ b/Framework/OverwatchTranscript/EventBucket.cs
@@ -2,15 +2,14 @@
 
 namespace OverwatchTranscript
 {
-    public class EventBucket
+    public class EventBucket : IFinalizedBucket
     {
         private const int MaxCount = 10000;
         private const int MaxBuffer = 100;
 
         private readonly object _lock = new object();
-        private readonly object _counterLock = new object();
         private bool closed = false;
-        private int pendingAdds = 0;
+
         private readonly string bucketFile;
         private readonly List<EventBucketEntry> buffer = new List<EventBucketEntry>();
         private EventBucketEntry? topEntry;
@@ -28,24 +27,26 @@ namespace OverwatchTranscript
         public bool IsFull { get; private set; }
         public DateTime EarliestUtc { get; private set; }
         public DateTime LatestUtc { get; private set; }
-        public string Error { get; private set; } = string.Empty;
 
         public void Add(DateTime utc, object payload)
         {
-            if (closed) throw new Exception("Already closed");
-            AddPending();
-            Task.Run(() => InternalAdd(utc, payload));
-        }
-
-        public void FinalizeBucket()
-        {
-            closed = true;
             lock (_lock)
             {
-                WaitForZeroPending();
+                if (closed) throw new Exception("Already closed");
+                AddToBuffer(utc, payload);
+                BufferToFile();
+            }
+        }
+
+        public IFinalizedBucket FinalizeBucket()
+        {
+            lock (_lock)
+            {
+                closed = true;
                 BufferToFile();
                 SortFileByTimestamps();
             }
+            return this;
         }
 
         public EventBucketEntry? ViewTopEntry()
@@ -70,43 +71,11 @@ namespace OverwatchTranscript
             }
         }
 
-        private void InternalAdd(DateTime utc, object payload)
-        {
-            lock (_lock)
-            {
-                AddToBuffer(utc, payload);
-                BufferToFile();
-                RemovePending();
-            }
-        }
-
-        private void BufferToFile()
-        {
-            if (buffer.Count > MaxBuffer)
-            {
-                using var file = File.Open(bucketFile, FileMode.Append);
-                using var writer = new StreamWriter(file);
-                foreach (var entry in buffer)
-                {
-                    writer.WriteLine(JsonConvert.SerializeObject(entry));
-                }
-                buffer.Clear();
-            }
-        }
-
         private void AddToBuffer(DateTime utc, object payload)
         {  
             var typeName = payload.GetType().FullName;
-            if (string.IsNullOrEmpty(typeName))
-            {
-                Error += "Empty typename for payload";
-                return;
-            }
-            if (utc == default)
-            {
-                Error += "DateTimeUtc not set";
-                return;
-            }
+            if (string.IsNullOrEmpty(typeName)) throw new Exception("Empty typename for payload");
+            if (utc == default) throw new Exception("DateTimeUtc not set");
 
             var entry = new EventBucketEntry
             {
@@ -126,6 +95,20 @@ namespace OverwatchTranscript
             buffer.Add(entry);
         }
 
+        private void BufferToFile()
+        {
+            if (buffer.Count > MaxBuffer)
+            {
+                using var file = File.Open(bucketFile, FileMode.Append);
+                using var writer = new StreamWriter(file);
+                foreach (var entry in buffer)
+                {
+                    writer.WriteLine(JsonConvert.SerializeObject(entry));
+                }
+                buffer.Clear();
+            }
+        }
+
         private void SortFileByTimestamps()
         {
             var lines = File.ReadAllLines(bucketFile);
@@ -139,35 +122,16 @@ namespace OverwatchTranscript
 
             topEntry = entries.First();
         }
+    }
 
-        private void AddPending()
-        {
-            lock (_counterLock)
-            {
-                pendingAdds++;
-            }
-        }
-
-        private void RemovePending()
-        {
-            lock (_counterLock)
-            {
-                pendingAdds--;
-                if (pendingAdds < 0) Error += "Pending less than zero";
-            }
-        }
-
-        private void WaitForZeroPending()
-        {
-            while (true)
-            {
-                lock (_counterLock)
-                {
-                    if (pendingAdds == 0) return;
-                }
-                Thread.Sleep(10);
-            }
-        }
+    public interface IFinalizedBucket
+    {
+        int Count { get; }
+        bool IsFull { get; }
+        DateTime EarliestUtc { get; }
+        DateTime LatestUtc { get; }
+        EventBucketEntry? ViewTopEntry();
+        void PopTopEntry();
     }
 
     [Serializable]
diff --git a/Framework/OverwatchTranscript/Model.cs b/Framework/OverwatchTranscript/Model.cs
index 08beda85..3854b997 100644
--- a/Framework/OverwatchTranscript/Model.cs
+++ b/Framework/OverwatchTranscript/Model.cs
@@ -4,7 +4,17 @@
     public class OverwatchTranscript
     {
         public OverwatchHeader Header { get; set; } = new();
-        public OverwatchMoment[] Moments { get; set; } = Array.Empty<OverwatchMoment>();
+        public OverwatchMomentReference[] MomentReferences { get; set; } = Array.Empty<OverwatchMomentReference>();
+    }
+
+    [Serializable]
+    public class OverwatchMomentReference
+    {
+        public string MomentsFile { get; set; } = string.Empty;
+        public int NumberOfMoments { get; set; }
+        public int NumberOfEvents { get; set; }
+        public DateTime EarliestUtc { get; set; }
+        public DateTime LatestUtc { get; set; }
     }
 
     [Serializable]
diff --git a/Framework/OverwatchTranscript/MomentReader.cs b/Framework/OverwatchTranscript/MomentReader.cs
new file mode 100644
index 00000000..e30d4f66
--- /dev/null
+++ b/Framework/OverwatchTranscript/MomentReader.cs
@@ -0,0 +1,90 @@
+using Newtonsoft.Json;
+
+namespace OverwatchTranscript
+{
+    public class MomentReader
+    {
+        private readonly OverwatchTranscript model;
+        private readonly string workingDir;
+        private int referenceIndex = 0;
+        private int momentsRead = 0;
+        private OpenReference currentRef;
+
+        public MomentReader(OverwatchTranscript model, string workingDir)
+        {
+            this.model = model;
+            this.workingDir = workingDir;
+
+            currentRef = CreateOpenReference();
+        }
+
+        public OverwatchMoment? Next()
+        {
+            if (referenceIndex >= model.MomentReferences.Length) return null;
+
+            var moment = currentRef.ReadNext();
+            if (moment == null)
+            {
+                currentRef.Close();
+                currentRef = null!;
+
+                // This reference file ran out.
+                // The number of moments read should match exactly the number of moments
+                // describe in the reference. If not, error:
+                var expected = model.MomentReferences[referenceIndex].NumberOfMoments;
+                if (momentsRead != expected)
+                {
+                    throw new Exception("Number of moments read from referenced file does not match number of moments value in model. " +
+                        $"Reads: { momentsRead} - model.MomentReferences[{referenceIndex}].NumberOfMoment: {expected}"); 
+                }
+
+                referenceIndex++;
+                if (referenceIndex < model.MomentReferences.Length)
+                {
+                    currentRef = CreateOpenReference();
+                }
+                momentsRead = 0;
+                return Next();
+            }
+            else
+            {
+                momentsRead++;
+                return moment;
+            }
+        }
+
+        private OpenReference CreateOpenReference()
+        {
+            var filepath = Path.Combine(workingDir, model.MomentReferences[referenceIndex].MomentsFile);
+            return new OpenReference(filepath);
+        }
+
+        private class OpenReference
+        {
+            private readonly FileStream file;
+            private readonly StreamReader reader;
+
+            public OpenReference(string filePath)
+            {
+                file = File.OpenRead(filePath);
+                reader = new StreamReader(file);
+            }
+
+            public OverwatchMoment? ReadNext()
+            {
+                var line = reader.ReadLine();
+                if (string.IsNullOrEmpty(line)) return null;
+                return JsonConvert.DeserializeObject<OverwatchMoment>(line);
+            }
+
+            public void Close()
+            {
+                reader.Close();
+                file.Close();
+
+                reader.Dispose();
+                file.Dispose();
+            }
+        }
+    }
+}
diff --git a/Framework/OverwatchTranscript/MomentReferenceBuilder.cs b/Framework/OverwatchTranscript/MomentReferenceBuilder.cs
new file mode 100644
index 00000000..d94a7dac
--- /dev/null
+++ b/Framework/OverwatchTranscript/MomentReferenceBuilder.cs
@@ -0,0 +1,122 @@
+using Newtonsoft.Json;
+
+namespace OverwatchTranscript
+{
+    public class MomentReferenceBuilder
+    {
+        private const int MaxMomentsPerReference = 100;
+        private readonly string workingDir;
+
+        public MomentReferenceBuilder(string workingDir)
+        {
+            this.workingDir = workingDir;
+        }
+
+        public OverwatchMomentReference[] Build(IFinalizedBucket[] buckets)
+        {
+            var result = new List<OverwatchMomentReference>();
+
+            var currentBuilder = new Builder(workingDir);
+
+            while (EntriesRemaining(buckets))
+            {
+                var earliestUtc = GetEarliestUtc(buckets);
+                var entries = CollectAllEntriesForUtc(earliestUtc, buckets);
+                var moment = ConvertEntriesToMoment(entries);
+                currentBuilder.Add(moment);
+                if (currentBuilder.NumberOfMoments == MaxMomentsPerReference)
+                {
+                    result.Add(currentBuilder.Build());
+                    currentBuilder = new Builder(workingDir);
+                }
+            }
+
+            return result.ToArray();
+        }
+
+        private OverwatchMoment ConvertEntriesToMoment(List<EventBucketEntry> entries)
+        {
+            var discintUtc = entries.Select(e => e.Utc).Distinct().ToArray();
+            if (discintUtc.Length != 1) throw new Exception("UTC mixing in moment construction.");
+
+            return new OverwatchMoment
+            {
+                Utc = entries[0].Utc,
+                Events = entries.Select(e => e.Event).ToArray()
+            };
+        }
+
+        private List<EventBucketEntry> CollectAllEntriesForUtc(DateTime earliestUtc, IFinalizedBucket[] buckets)
+        {
+            var result = new List<EventBucketEntry>();
+
+            foreach (var bucket in buckets)
+            {
+                var top = bucket.ViewTopEntry();
+                while (top != null && top.Utc == earliestUtc)
+                {
+                    result.Add(top);
+                    bucket.PopTopEntry();
+                    top = bucket.ViewTopEntry();
+                }
+            }
+
+            return result;
+        }
+
+        private DateTime GetEarliestUtc(IFinalizedBucket[] buckets)
+        {
+            var earliest = DateTime.MaxValue;
+            foreach (var bucket in buckets)
+            {
+                var top = bucket.ViewTopEntry();
+                if (top != null && top.Utc < earliest) earliest = top.Utc;
+            }
+            return earliest;
+        }
+
+        private bool EntriesRemaining(IFinalizedBucket[] buckets)
+        {
+            return buckets.Any(b => b.ViewTopEntry() != null);
+        }
+
+        public class Builder
+        {
+            private OverwatchMomentReference reference;
+
+            public Builder(string workingDir)
+            {
+                reference = new OverwatchMomentReference
+                {
+                    MomentsFile = Path.Combine(workingDir, Guid.NewGuid().ToString()),
+                    EarliestUtc = DateTime.MaxValue,
+                    LatestUtc = DateTime.MinValue,
+                    NumberOfEvents = 0,
+                    NumberOfMoments = 0,
+                };
+            }
+
+            public int NumberOfMoments => reference.NumberOfMoments;
+
+            public void Add(OverwatchMoment moment)
+            {
+                File.AppendAllLines(reference.MomentsFile, new[]
+                {
+                    JsonConvert.SerializeObject(moment)
+                });
+
+                if (moment.Utc < reference.EarliestUtc) reference.EarliestUtc = moment.Utc;
+                if (moment.Utc > reference.LatestUtc) reference.LatestUtc = moment.Utc;
+                reference.NumberOfMoments++;
+                reference.NumberOfEvents += moment.Events.Length;
+            }
+
+            public OverwatchMomentReference Build()
+            {
+                var result = reference;
+                reference = null!;
+                return result;
+            }
+        }
+    }
+}
diff --git a/Framework/OverwatchTranscript/TranscriptReader.cs b/Framework/OverwatchTranscript/TranscriptReader.cs
index ddfaec35..70fa00e2 100644
--- a/Framework/OverwatchTranscript/TranscriptReader.cs
+++ b/Framework/OverwatchTranscript/TranscriptReader.cs
@@ -25,9 +25,12 @@ namespace OverwatchTranscript
         private readonly List<Action<ActivateMoment>> momentHandlers = new List<Action<ActivateMoment>>();
         private readonly Dictionary<string, List<Action<ActivateMoment, string>>> eventHandlers = new Dictionary<string, List<Action<ActivateMoment, string>>>();
         private readonly string workingDir;
-        private OverwatchTranscript model = null!;
-        private long momentIndex = 0;
+        private readonly OverwatchTranscript model;
+        private readonly MomentReader reader;
         private bool closed;
+        private long momentCounter;
+        private readonly object queueLock = new object();
+        private readonly List<OverwatchMoment> queue = new List<OverwatchMoment>();
 
         public TranscriptReader(string workingDir, string inputFilename)
         {
@@ -39,7 +42,8 @@ namespace OverwatchTranscript
             if (!Directory.Exists(workingDir)) Directory.CreateDirectory(workingDir);
             if (File.Exists(transcriptFile) || Directory.Exists(artifactsFolder)) throw new Exception("workingdir not clean");
 
-            LoadModel(inputFilename);
+            model = LoadModel(inputFilename);
+            reader = new MomentReader(model, workingDir);
         }
 
         public OverwatchCommonHeader Header
@@ -93,14 +97,15 @@ namespace OverwatchTranscript
         public void Next()
         {
             CheckClosed();
-            if (momentIndex >= model.Moments.Length) return;
+            OverwatchMoment moment = null!;
+            lock (queueLock)
+            {
+                if (queue.Count == 0) return;
+                moment = queue[0];
+                queue.RemoveAt(0);
+            }
 
-            var moment = model.Moments[momentIndex];
-            var momentDuration = GetMomentDuration();
-
-            ActivateMoment(moment, momentDuration, momentIndex);
-
-            momentIndex++;
+            ActivateMoment(moment);
         }
 
         public void Close()
@@ -120,12 +125,10 @@ namespace OverwatchTranscript
 
         private TimeSpan? GetMomentDuration()
         {
-            if (momentIndex < 0) throw new Exception("Index < 0");
-            if (momentIndex + 1 >= model.Moments.Length) return null;
+            if (current == null) return null;
+            if (next == null) return null;
 
-            return
-                model.Moments[momentIndex + 1].Utc -
-                model.Moments[momentIndex].Utc;
+            return next.Utc - current.Utc;
         }
 
         private void ActivateMoment(OverwatchMoment moment, TimeSpan? duration, long momentIndex)
@@ -162,7 +165,7 @@ namespace OverwatchTranscript
             }
         }
 
-        private void LoadModel(string inputFilename)
+        private OverwatchTranscript LoadModel(string inputFilename)
         {
             ZipFile.ExtractToDirectory(inputFilename, workingDir);
 
@@ -172,7 +175,7 @@ namespace OverwatchTranscript
                 throw new Exception("Is not a transcript file. Unzipped to: " + workingDir);
             }
 
-            model = JsonConvert.DeserializeObject<OverwatchTranscript>(File.ReadAllText(transcriptFile))!;
+            return JsonConvert.DeserializeObject<OverwatchTranscript>(File.ReadAllText(transcriptFile))!;
         }
 
         private void CheckClosed()
diff --git a/Framework/OverwatchTranscript/TranscriptWriter.cs b/Framework/OverwatchTranscript/TranscriptWriter.cs
index 4fdc260d..f5defa3b 100644
--- a/Framework/OverwatchTranscript/TranscriptWriter.cs
+++ b/Framework/OverwatchTranscript/TranscriptWriter.cs
@@ -14,10 +14,11 @@ namespace OverwatchTranscript
     public class TranscriptWriter : ITranscriptWriter
     {
         private readonly object _lock = new object();
+        private readonly MomentReferenceBuilder builder;
         private readonly string transcriptFile;
         private readonly string artifactsFolder;
         private readonly Dictionary<string, string> header = new Dictionary<string, string>();
-        private readonly SortedList<DateTime, List<OverwatchEvent>> buffer = new SortedList<DateTime, List<OverwatchEvent>>();
+        private readonly BucketSet bucketSet;
         private readonly string workingDir;
         private bool closed;
 
@@ -25,6 +26,8 @@ namespace OverwatchTranscript
         {
             closed = false;
             this.workingDir = workingDir;
+            bucketSet = new BucketSet(workingDir);
+            builder = new MomentReferenceBuilder(workingDir);
             transcriptFile = Path.Combine(workingDir, TranscriptConstants.TranscriptFilename);
             artifactsFolder = Path.Combine(workingDir, TranscriptConstants.ArtifactFolderName);
 
@@ -35,27 +38,7 @@ namespace OverwatchTranscript
         public void Add(DateTime utc, object payload)
         {
             CheckClosed();
-            var typeName = payload.GetType().FullName;
-            if (string.IsNullOrEmpty(typeName)) throw new Exception("Empty typename for payload");
-            if (utc == default) throw new Exception("DateTimeUtc not set");
-
-            var newEvent = new OverwatchEvent
-            {
-                Type = typeName,
-                Payload = JsonConvert.SerializeObject(payload)
-            };
-
-            lock (_lock)
-            {
-                if (buffer.ContainsKey(utc))
-                {
-                    buffer[utc].Add(newEvent);
-                }
-                else
-                {
-                    buffer.Add(utc, new List<OverwatchEvent> { newEvent });
-                }
-            }
+            bucketSet.Add(utc, payload);
         }
 
         public void AddHeader(string key, object value)
@@ -78,12 +61,17 @@ namespace OverwatchTranscript
 
         public void Write(string outputFilename)
         {
-            if (!buffer.Any()) throw new Exception("No entries added.");
+            if (bucketSet.IsEmpty()) throw new Exception("No entries added.");
+            if (!string.IsNullOrEmpty(bucketSet.Error))
+            {
+                throw new Exception("Exceptions in BucketSet: " + bucketSet.Error);
+            }
 
             CheckClosed();
             closed = true;
 
-            var model = CreateModel();
+            var momentReferences = builder.Build(bucketSet.FinalizeBuckets());
+            var model = CreateModel(momentReferences);
 
             File.WriteAllText(transcriptFile, JsonConvert.SerializeObject(model, Formatting.Indented));
 
@@ -92,7 +80,7 @@ namespace OverwatchTranscript
             Directory.Delete(workingDir, true);
         }
 
-        private OverwatchTranscript CreateModel()
+        private OverwatchTranscript CreateModel(OverwatchMomentReference[] momentReferences)
         {
             lock (_lock)
             {
@@ -100,7 +88,7 @@ namespace OverwatchTranscript
                 {
                     Header = new OverwatchHeader
                     {
-                        Common = CreateCommonHeader(),
+                        Common = CreateCommonHeader(momentReferences),
                         Entries = header.Select(h =>
                         {
                             return new OverwatchHeaderEntry
@@ -110,31 +98,27 @@ namespace OverwatchTranscript
                             };
                         }).ToArray()
                     },
-                    Moments = buffer.Select(p =>
-                    {
-                        return new OverwatchMoment
-                        {
-                            Utc = p.Key,
-                            Events = p.Value.ToArray()
-                        };
-                    }).ToArray()
+                    MomentReferences = momentReferences
                 };
 
                 header.Clear();
-                buffer.Clear();
-
                 return model;
             }
         }
 
-        private OverwatchCommonHeader CreateCommonHeader()
+        private OverwatchCommonHeader CreateCommonHeader(OverwatchMomentReference[] momentReferences)
         {
+            var moments = momentReferences.Sum(m => m.NumberOfMoments);
+            var events = momentReferences.Sum(m => m.NumberOfEvents);
+            var earliest = momentReferences.Min(m => m.EarliestUtc);
+            var latest = momentReferences.Max(m => m.LatestUtc);
+
             return new OverwatchCommonHeader
             {
-                NumberOfMoments = buffer.Count,
-                NumberOfEvents = buffer.Sum(e => e.Value.Count),
-                EarliestUtc = buffer.Min(e => e.Key),
-                LatestUtc = buffer.Max(e => e.Key)
+                NumberOfMoments = moments,
+                NumberOfEvents = events,
+                EarliestUtc = earliest,
+                LatestUtc = latest
             };
         }