diff --git a/AccessQueueService/AccessQueueService.csproj b/AccessQueueService/AccessQueueService.csproj
index 9c50d6d..dac5a84 100644
--- a/AccessQueueService/AccessQueueService.csproj
+++ b/AccessQueueService/AccessQueueService.csproj
@@ -1,17 +1,21 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
-  <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
-    <Nullable>enable</Nullable>
-    <ImplicitUsings>enable</ImplicitUsings>
-  </PropertyGroup>
+	<PropertyGroup>
+		<TargetFramework>net8.0</TargetFramework>
+		<Nullable>enable</Nullable>
+		<ImplicitUsings>enable</ImplicitUsings>
+	</PropertyGroup>
 
-  <ItemGroup>
-    <PackageReference Include="Serilog.AspNetCore" Version="9.0.0" />
-    <PackageReference Include="Serilog.Settings.Configuration" Version="9.0.0" />
-    <PackageReference Include="Serilog.Sinks.Console" Version="6.0.0" />
-    <PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
-    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />
-  </ItemGroup>
+	<ItemGroup>
+		<PackageReference Include="Serilog.AspNetCore" Version="9.0.0" />
+		<PackageReference Include="Serilog.Settings.Configuration" Version="9.0.0" />
+		<PackageReference Include="Serilog.Sinks.Console" Version="6.0.0" />
+		<PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
+		<PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />
+	</ItemGroup>
+
+	<ItemGroup>
+		<InternalsVisibleTo Include="AccessQueueServiceTests" />
+	</ItemGroup>
 
 </Project>
diff --git a/AccessQueueService/Data/TakeANumberAccessQueueRepo.cs b/AccessQueueService/Data/TakeANumberAccessQueueRepo.cs
index 5b35204..7289845 100644
--- a/AccessQueueService/Data/TakeANumberAccessQueueRepo.cs
+++ b/AccessQueueService/Data/TakeANumberAccessQueueRepo.cs
@@ -6,11 +6,11 @@ namespace AccessQueueService.Data
     public class TakeANumberAccessQueueRepo : IAccessQueueRepo
     {
         private readonly Dictionary<string, AccessTicket> _accessTickets = [];
-        private readonly Dictionary<string, ulong> _queueNumbers = [];
-        private readonly Dictionary<ulong, AccessTicket> _accessQueue = [];
+        private Dictionary<string, ulong> _queueNumbers = [];
+        private Dictionary<ulong, AccessTicket> _accessQueue = [];
 
-        private ulong _nowServing = 0;
-        private ulong _nextUnusedTicket = 0; 
+        internal ulong _nowServing = 0;
+        internal ulong _nextUnusedTicket = 0; 
 
         public int GetUnexpiredTicketsCount() => _accessTickets.Count(t => t.Value.ExpiresOn > DateTime.UtcNow);
         public int GetActiveTicketsCount(DateTime activeCutoff) => _accessTickets
@@ -32,6 +32,11 @@ namespace AccessQueueService.Data
 
         public void Enqueue(AccessTicket ticket)
         {
+            if(_nextUnusedTicket >= long.MaxValue)
+            {
+                // Prevent overflow
+                Optimize();
+            }
             _queueNumbers[ticket.UserId] = _nextUnusedTicket;
             _accessQueue[_nextUnusedTicket] = ticket;
             _nextUnusedTicket++;
@@ -105,10 +110,8 @@ namespace AccessQueueService.Data
             return _accessTickets.Remove(userId);
         }
 
-        public void Optimize()
+        internal void Optimize()
         {
-            DeleteExpiredTickets();
-
             var newQueue = new Dictionary<ulong, AccessTicket>();
             var newQueueNumbers = new Dictionary<string, ulong>();
             ulong newIndex = 0;
@@ -116,8 +119,12 @@ namespace AccessQueueService.Data
             {
                 var user = _accessQueue[i];
                 newQueue[newIndex] = user;
-                newQueueNumbers[user.UserId] = newIndex;
+                newQueueNumbers[user.UserId] = newIndex++;
             }
+            _accessQueue = newQueue;
+            _queueNumbers = newQueueNumbers;
+            _nowServing = 0;
+            _nextUnusedTicket = newIndex;
         }
     }
 }
diff --git a/AccessQueueServiceTests/AccessQueueRepoTests.cs b/AccessQueueServiceTests/AccessQueueRepoTests.cs
index a24fa1e..f80a9a3 100644
--- a/AccessQueueServiceTests/AccessQueueRepoTests.cs
+++ b/AccessQueueServiceTests/AccessQueueRepoTests.cs
@@ -22,7 +22,6 @@ namespace AccessQueueServiceTests
         [Fact]
         public void GetUnexpiredTicketsCount_ReturnsCorrectCount()
         {
-
             _repo.UpsertTicket(new AccessTicket { UserId = "a", ExpiresOn = DateTime.UtcNow.AddMinutes(1), LastActive = DateTime.UtcNow });
             _repo.UpsertTicket(new AccessTicket { UserId = "b", ExpiresOn = DateTime.UtcNow.AddMinutes(-1), LastActive = DateTime.UtcNow });
             Assert.Equal(1, _repo.GetUnexpiredTicketsCount());
@@ -192,5 +191,49 @@ namespace AccessQueueServiceTests
             Assert.Null(_repo.GetTicket("second"));
             Assert.Null(_repo.GetTicket("third"));
         }
+
+        [Fact]
+        public void Optimize_MaintainsQueueOrder()
+        {
+            var ticket1 = new AccessTicket { UserId = "first", ExpiresOn = DateTime.UtcNow.AddMinutes(1), LastActive = DateTime.UtcNow };
+            var ticket2 = new AccessTicket { UserId = "second", ExpiresOn = DateTime.UtcNow.AddMinutes(1), LastActive = DateTime.UtcNow };
+            var ticket3 = new AccessTicket { UserId = "third", ExpiresOn = DateTime.UtcNow.AddMinutes(1), LastActive = DateTime.UtcNow };
+            _repo.Enqueue(ticket1);
+            _repo.Enqueue(ticket2);
+            _repo.Enqueue(ticket3);
+
+            _repo.DidDequeueUntilFull(60 * 60, 60, 1);
+            _repo.Optimize();
+
+            Assert.NotNull(_repo.GetTicket("first"));
+            Assert.Equal(0, _repo.GetRequestsAhead("second"));
+            Assert.Equal(1, _repo.GetRequestsAhead("third"));
+            Assert.Equal(0ul, _repo._nowServing);
+
+            _repo.DidDequeueUntilFull(60 * 60, 60, 2);
+            Assert.NotNull(_repo.GetTicket("second"));
+            Assert.Equal(0, _repo.GetRequestsAhead("third"));
+        }
+
+        [Fact]
+        public void Enqueue_MaintainsQueueOrder_WhenMaxValueExceeded()
+        {
+            var ticket1 = new AccessTicket { UserId = "first", ExpiresOn = DateTime.UtcNow.AddMinutes(1), LastActive = DateTime.UtcNow };
+            var ticket2 = new AccessTicket { UserId = "second", ExpiresOn = DateTime.UtcNow.AddMinutes(1), LastActive = DateTime.UtcNow };
+            var ticket3 = new AccessTicket { UserId = "third", ExpiresOn = DateTime.UtcNow.AddMinutes(1), LastActive = DateTime.UtcNow };
+
+            _repo._nowServing = long.MaxValue - 1;
+            _repo._nextUnusedTicket = long.MaxValue - 1;
+
+            _repo.Enqueue(ticket1);
+            _repo.Enqueue(ticket2);
+            _repo.Enqueue(ticket3);
+
+            Assert.Equal(0ul, _repo._nowServing);
+            Assert.Equal(3ul, _repo._nextUnusedTicket);
+
+            Assert.Equal(0, _repo.GetRequestsAhead("first"));
+            Assert.Equal(2, _repo.GetRequestsAhead("third"));
+        }
     }
 }