diff --git a/src/ServiceControl.Audit.Persistence.RavenDB/DatabaseSetup.cs b/src/ServiceControl.Audit.Persistence.RavenDB/DatabaseSetup.cs
index 59675cc062..6010e227fd 100644
--- a/src/ServiceControl.Audit.Persistence.RavenDB/DatabaseSetup.cs
+++ b/src/ServiceControl.Audit.Persistence.RavenDB/DatabaseSetup.cs
@@ -46,6 +46,8 @@ await documentStore.Maintenance.Server
                 new SagaDetailsIndex()
             };
 
+            await DeleteLegacySagaDetailsIndex(documentStore, cancellationToken);
+
             if (configuration.EnableFullTextSearch)
             {
                 indexList.Add(new MessagesViewIndexWithFullTextSearch());
@@ -69,6 +71,22 @@ await documentStore.Maintenance
             await documentStore.Maintenance.SendAsync(new ConfigureExpirationOperation(expirationConfig), cancellationToken);
         }
 
+        public static async Task DeleteLegacySagaDetailsIndex(IDocumentStore documentStore, CancellationToken cancellationToken)
+        {
+            // If the SagaDetailsIndex exists but does not have a .Take(50000), then we remove the current SagaDetailsIndex and
+            // create a new one. If we do not remove the current one, then RavenDB will attempt to do a side-by-side migration.
+            // Doing a side-by-side migration results in the index never swapping if there is constant ingestion as RavenDB will wait.
+            // for the index to not be stale before swapping to the new index. Constant ingestion means the index will never be not-stale.
+            // This needs to stay in place until the next major version as the user could upgrade from an older version of the current
+            // Major (v5.x.x) which might still have the incorrect index.
+            var sagaDetailsIndexOperation = new GetIndexOperation("SagaDetailsIndex");
+            var sagaDetailsIndexDefinition = await documentStore.Maintenance.SendAsync(sagaDetailsIndexOperation, cancellationToken);
+            if (sagaDetailsIndexDefinition != null && !sagaDetailsIndexDefinition.Reduce.Contains("Take(50000)"))
+            {
+                await documentStore.Maintenance.SendAsync(new DeleteIndexOperation("SagaDetailsIndex"), cancellationToken);
+            }
+        }
+
         readonly DatabaseConfiguration configuration;
     }
 }
diff --git a/src/ServiceControl.Audit.Persistence.RavenDB/Indexes/SagaDetailsIndex.cs b/src/ServiceControl.Audit.Persistence.RavenDB/Indexes/SagaDetailsIndex.cs
index 05222d3f11..b6dec541a0 100644
--- a/src/ServiceControl.Audit.Persistence.RavenDB/Indexes/SagaDetailsIndex.cs
+++ b/src/ServiceControl.Audit.Persistence.RavenDB/Indexes/SagaDetailsIndex.cs
@@ -53,6 +53,7 @@ into g
                     SagaType = first.SagaType,
                     Changes = g.SelectMany(x => x.Changes)
                         .OrderByDescending(x => x.FinishTime)
+                        .Take(50000)
                         .ToList()
                 };
 
diff --git a/src/ServiceControl.Audit.Persistence.Tests.RavenDB/SagaDetailsIndexTests.cs b/src/ServiceControl.Audit.Persistence.Tests.RavenDB/SagaDetailsIndexTests.cs
new file mode 100644
index 0000000000..ffa30919ed
--- /dev/null
+++ b/src/ServiceControl.Audit.Persistence.Tests.RavenDB/SagaDetailsIndexTests.cs
@@ -0,0 +1,123 @@
+namespace ServiceControl.Audit.Persistence.Tests
+{
+    using System;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using NUnit.Framework;
+    using Raven.Client.Documents.Indexes;
+    using Raven.Client.Documents.Operations.Indexes;
+    using ServiceControl.SagaAudit;
+
+    [TestFixture]
+    class SagaDetailsIndexTests : PersistenceTestFixture
+    {
+        [Test]
+        public async Task Deletes_index_that_does_not_have_cap_of_50000()
+        {
+            await configuration.DocumentStore.Maintenance.SendAsync(new DeleteIndexOperation("SagaDetailsIndex"));
+
+            var indexWithout50000capDefinition = new IndexDefinition
+            {
+                Name = "SagaDetailsIndex",
+                Maps = new System.Collections.Generic.HashSet<string>
+                            {
+                                @"from doc in docs
+                                                     select new
+                                                     {
+                                                         doc.SagaId,
+                                                         Id = doc.SagaId,
+                                                         doc.SagaType,
+                                                         Changes = new[]
+                                                         {
+                                    new
+                                    {
+                                        Endpoint = doc.Endpoint,
+                                        FinishTime = doc.FinishTime,
+                                        InitiatingMessage = doc.InitiatingMessage,
+                                        OutgoingMessages = doc.OutgoingMessages,
+                                        StartTime = doc.StartTime,
+                                        StateAfterChange = doc.StateAfterChange,
+                                        Status = doc.Status
+                                    }
+                                }
+            }"
+                            },
+                Reduce = @"from result in results
+                                            group result by result.SagaId
+                            into g
+                                            let first = g.First()
+                                            select new
+                                            {
+                                                Id = first.SagaId,
+                                                SagaId = first.SagaId,
+                                                SagaType = first.SagaType,
+                                                Changes = g.SelectMany(x => x.Changes)
+                                                    .OrderByDescending(x => x.FinishTime)
+                                                    .ToList()
+                                            }"
+            };
+
+            var putIndexesOp = new PutIndexesOperation(indexWithout50000capDefinition);
+
+            await configuration.DocumentStore.Maintenance.SendAsync(putIndexesOp);
+
+            var sagaDetailsIndexOperation = new GetIndexOperation("SagaDetailsIndex");
+            var sagaDetailsIndexDefinition = await configuration.DocumentStore.Maintenance.SendAsync(sagaDetailsIndexOperation);
+
+            Assert.IsNotNull(sagaDetailsIndexDefinition);
+
+            await Persistence.RavenDB.DatabaseSetup.DeleteLegacySagaDetailsIndex(configuration.DocumentStore, CancellationToken.None);
+
+            sagaDetailsIndexDefinition = await configuration.DocumentStore.Maintenance.SendAsync(sagaDetailsIndexOperation);
+
+            Assert.IsNull(sagaDetailsIndexDefinition);
+        }
+
+        [Test]
+        public async Task Does_not_delete_index_that_does_have_cap_of_50000()
+        {
+            await Persistence.RavenDB.DatabaseSetup.DeleteLegacySagaDetailsIndex(configuration.DocumentStore, CancellationToken.None);
+
+            var sagaDetailsIndexOperation = new GetIndexOperation("SagaDetailsIndex");
+            var sagaDetailsIndexDefinition = await configuration.DocumentStore.Maintenance.SendAsync(sagaDetailsIndexOperation);
+
+            Assert.IsNotNull(sagaDetailsIndexDefinition);
+        }
+
+        [Test]
+        public async Task Should_only_reduce_the_last_50000_saga_state_changes()
+        {
+            var sagaType = "MySagaType";
+            var sagaState = "some-saga-state";
+
+            await IngestSagaAudits(new SagaSnapshot
+            {
+                SagaId = Guid.NewGuid(),
+                SagaType = sagaType,
+                Status = SagaStateChangeStatus.New,
+                StateAfterChange = sagaState
+            });
+
+            await configuration.CompleteDBOperation();
+
+            using (var session = configuration.DocumentStore.OpenAsyncSession())
+            {
+                var sagaDetailsIndexOperation = new GetIndexOperation("SagaDetailsIndex");
+                var sagaDetailsIndexDefinition = await configuration.DocumentStore.Maintenance.SendAsync(sagaDetailsIndexOperation);
+
+                Assert.IsTrue(sagaDetailsIndexDefinition.Reduce.Contains("Take(50000)"), "The SagaDetails index definition does not contain a .Take(50000) to limit the number of saga state changes that are reduced by the map/reduce");
+            }
+        }
+
+        async Task IngestSagaAudits(params SagaSnapshot[] snapshots)
+        {
+            var unitOfWork = StartAuditUnitOfWork(snapshots.Length);
+            foreach (var snapshot in snapshots)
+            {
+                await unitOfWork.RecordSagaSnapshot(snapshot);
+            }
+            await unitOfWork.DisposeAsync();
+            await configuration.CompleteDBOperation();
+        }
+    }
+}
\ No newline at end of file