diff --git a/Backend.Tests/Controllers/MergeControllerTests.cs b/Backend.Tests/Controllers/MergeControllerTests.cs
index 85e797f7e2..26864e52cb 100644
--- a/Backend.Tests/Controllers/MergeControllerTests.cs
+++ b/Backend.Tests/Controllers/MergeControllerTests.cs
@@ -11,6 +11,7 @@ namespace Backend.Tests.Controllers
 {
     public class MergeControllerTests : IDisposable
     {
+        private IMongoDbContext _mongoDbContext = null!;
         private IMergeBlacklistRepository _mergeBlacklistRepo = null!;
         private IMergeGraylistRepository _mergeGraylistRepo = null!;
         private IWordRepository _wordRepo = null!;
@@ -38,11 +39,13 @@ protected virtual void Dispose(bool disposing)
         [SetUp]
         public void Setup()
         {
+            _mongoDbContext = new MongoDbContextMock();
             _mergeBlacklistRepo = new MergeBlacklistRepositoryMock();
             _mergeGraylistRepo = new MergeGraylistRepositoryMock();
             _wordRepo = new WordRepositoryMock();
             _wordService = new WordService(_wordRepo);
-            _mergeService = new MergeService(_mergeBlacklistRepo, _mergeGraylistRepo, _wordRepo, _wordService);
+            _mergeService = new MergeService(
+                _mongoDbContext, _mergeBlacklistRepo, _mergeGraylistRepo, _wordRepo, _wordService);
             _permissionService = new PermissionServiceMock();
             _mergeController = new MergeController(_mergeService, _permissionService);
         }
diff --git a/Backend.Tests/Mocks/MongoDbContextMock.cs b/Backend.Tests/Mocks/MongoDbContextMock.cs
new file mode 100644
index 0000000000..cbc3b028a7
--- /dev/null
+++ b/Backend.Tests/Mocks/MongoDbContextMock.cs
@@ -0,0 +1,32 @@
+using System;
+using System.Threading.Tasks;
+using BackendFramework.Interfaces;
+using MongoDB.Driver;
+
+namespace Backend.Tests.Mocks;
+
+public class MongoDbContextMock : IMongoDbContext
+{
+    public IMongoDatabase Db => throw new NotSupportedException();
+    public Task<IMongoTransaction> BeginTransaction()
+    {
+        return Task.FromResult<IMongoTransaction>(new MongoTransactionMock());
+    }
+
+    private sealed class MongoTransactionMock : IMongoTransaction
+    {
+        public Task CommitTransactionAsync()
+        {
+            return Task.CompletedTask;
+        }
+
+        public Task AbortTransactionAsync()
+        {
+            return Task.CompletedTask;
+        }
+
+        public void Dispose()
+        {
+        }
+    }
+}
diff --git a/Backend.Tests/Services/MergeServiceTests.cs b/Backend.Tests/Services/MergeServiceTests.cs
index ab25ee2739..72bcbb5cba 100644
--- a/Backend.Tests/Services/MergeServiceTests.cs
+++ b/Backend.Tests/Services/MergeServiceTests.cs
@@ -10,6 +10,7 @@ namespace Backend.Tests.Services
 {
     public class MergeServiceTests
     {
+        private IMongoDbContext _mongoDbContext = null!;
         private IMergeBlacklistRepository _mergeBlacklistRepo = null!;
         private IMergeGraylistRepository _mergeGraylistRepo = null!;
         private IWordRepository _wordRepo = null!;
@@ -22,11 +23,13 @@ public class MergeServiceTests
         [SetUp]
         public void Setup()
         {
+            _mongoDbContext = new MongoDbContextMock();
             _mergeBlacklistRepo = new MergeBlacklistRepositoryMock();
             _mergeGraylistRepo = new MergeGraylistRepositoryMock();
             _wordRepo = new WordRepositoryMock();
             _wordService = new WordService(_wordRepo);
-            _mergeService = new MergeService(_mergeBlacklistRepo, _mergeGraylistRepo, _wordRepo, _wordService);
+            _mergeService = new MergeService(
+                _mongoDbContext, _mergeBlacklistRepo, _mergeGraylistRepo, _wordRepo, _wordService);
         }
 
         [Test]
diff --git a/Backend/Contexts/BannerContext.cs b/Backend/Contexts/BannerContext.cs
index ace2284f9f..15d123d25b 100644
--- a/Backend/Contexts/BannerContext.cs
+++ b/Backend/Contexts/BannerContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,14 +8,13 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class BannerContext : IBannerContext
     {
-        private readonly IMongoDatabase _db;
+        private readonly IMongoDbContext _mongoDbContext;
 
-        public BannerContext(IOptions<Startup.Settings> options)
+        public BannerContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<Banner> Banners => _db.GetCollection<Banner>("BannerCollection");
+        public IMongoCollection<Banner> Banners => _mongoDbContext.Db.GetCollection<Banner>("BannerCollection");
     }
 }
diff --git a/Backend/Contexts/MergeBlacklistContext.cs b/Backend/Contexts/MergeBlacklistContext.cs
index f977bf6d70..52c1c65f1c 100644
--- a/Backend/Contexts/MergeBlacklistContext.cs
+++ b/Backend/Contexts/MergeBlacklistContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,15 +8,13 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class MergeBlacklistContext : IMergeBlacklistContext
     {
-        private readonly IMongoDatabase _db;
-
-        public MergeBlacklistContext(IOptions<Startup.Settings> options)
+        private readonly IMongoDbContext _mongoDbContext;
+        public MergeBlacklistContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<MergeWordSet> MergeBlacklist => _db.GetCollection<MergeWordSet>(
+        public IMongoCollection<MergeWordSet> MergeBlacklist => _mongoDbContext.Db.GetCollection<MergeWordSet>(
             "MergeBlacklistCollection");
     }
 }
diff --git a/Backend/Contexts/MergeGraylistContext.cs b/Backend/Contexts/MergeGraylistContext.cs
index d9ea381829..35b0f8caf9 100644
--- a/Backend/Contexts/MergeGraylistContext.cs
+++ b/Backend/Contexts/MergeGraylistContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,15 +8,13 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class MergeGraylistContext : IMergeGraylistContext
     {
-        private readonly IMongoDatabase _db;
-
-        public MergeGraylistContext(IOptions<Startup.Settings> options)
+        private readonly IMongoDbContext _mongoDbContext;
+        public MergeGraylistContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<MergeWordSet> MergeGraylist => _db.GetCollection<MergeWordSet>(
+        public IMongoCollection<MergeWordSet> MergeGraylist => _mongoDbContext.Db.GetCollection<MergeWordSet>(
             "MergeGraylistCollection");
     }
 }
diff --git a/Backend/Contexts/MongoDbContext.cs b/Backend/Contexts/MongoDbContext.cs
new file mode 100644
index 0000000000..475c7cb3c7
--- /dev/null
+++ b/Backend/Contexts/MongoDbContext.cs
@@ -0,0 +1,49 @@
+using System.Threading.Tasks;
+using BackendFramework.Interfaces;
+using Microsoft.Extensions.Options;
+using MongoDB.Driver;
+
+namespace BackendFramework.Contexts;
+
+public class MongoDbContext : IMongoDbContext
+{
+    public IMongoDatabase Db { get; }
+
+    public MongoDbContext(IOptions<Startup.Settings> options)
+    {
+        var client = new MongoClient(options.Value.ConnectionString);
+        Db = client.GetDatabase(options.Value.CombineDatabase);
+    }
+
+    public async Task<IMongoTransaction> BeginTransaction()
+    {
+        var session = await Db.Client.StartSessionAsync();
+        session.StartTransaction();
+        return new MongoTransactionWrapper(session);
+    }
+
+    private class MongoTransactionWrapper : IMongoTransaction
+    {
+        private readonly IClientSessionHandle _session;
+
+        public MongoTransactionWrapper(IClientSessionHandle session)
+        {
+            _session = session;
+        }
+
+        public Task CommitTransactionAsync()
+        {
+            return _session.CommitTransactionAsync();
+        }
+
+        public Task AbortTransactionAsync()
+        {
+            return _session.AbortTransactionAsync();
+        }
+
+        public void Dispose()
+        {
+            _session.Dispose();
+        }
+    }
+}
diff --git a/Backend/Contexts/PasswordResetContext.cs b/Backend/Contexts/PasswordResetContext.cs
index dbcc4041c0..84aebc7eed 100644
--- a/Backend/Contexts/PasswordResetContext.cs
+++ b/Backend/Contexts/PasswordResetContext.cs
@@ -10,17 +10,16 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class PasswordResetContext : IPasswordResetContext
     {
-        private readonly IMongoDatabase _db;
+        private readonly IMongoDbContext _mongoDbContext;
         public int ExpireTime { get; }
 
-        public PasswordResetContext(IOptions<Startup.Settings> options)
+        public PasswordResetContext(IOptions<Startup.Settings> options, IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
             ExpireTime = options.Value.PassResetExpireTime;
         }
 
-        private IMongoCollection<PasswordReset> PasswordResets => _db.GetCollection<PasswordReset>(
+        private IMongoCollection<PasswordReset> PasswordResets => _mongoDbContext.Db.GetCollection<PasswordReset>(
             "PasswordResetCollection");
 
         public Task ClearAll(string email)
diff --git a/Backend/Contexts/ProjectContext.cs b/Backend/Contexts/ProjectContext.cs
index 696a8a35da..0901b6b0e4 100644
--- a/Backend/Contexts/ProjectContext.cs
+++ b/Backend/Contexts/ProjectContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,14 +8,12 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class ProjectContext : IProjectContext
     {
-        private readonly IMongoDatabase _db;
-
-        public ProjectContext(IOptions<Startup.Settings> options)
+        private readonly IMongoDbContext _mongoDbContext;
+        public ProjectContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<Project> Projects => _db.GetCollection<Project>("ProjectsCollection");
+        public IMongoCollection<Project> Projects => _mongoDbContext.Db.GetCollection<Project>("ProjectsCollection");
     }
 }
diff --git a/Backend/Contexts/SemanticDomainContext.cs b/Backend/Contexts/SemanticDomainContext.cs
index 5ad11cac28..66fa39acd0 100644
--- a/Backend/Contexts/SemanticDomainContext.cs
+++ b/Backend/Contexts/SemanticDomainContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,15 +8,13 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class SemanticDomainContext : ISemanticDomainContext
     {
-        private readonly IMongoDatabase _db;
-
-        public SemanticDomainContext(IOptions<Startup.Settings> options)
+        private readonly IMongoDbContext _mongoDbContext;
+        public SemanticDomainContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<SemanticDomainTreeNode> SemanticDomains => _db.GetCollection<SemanticDomainTreeNode>("SemanticDomainTree");
-        public IMongoCollection<SemanticDomainFull> FullSemanticDomains => _db.GetCollection<SemanticDomainFull>("SemanticDomains");
+        public IMongoCollection<SemanticDomainTreeNode> SemanticDomains => _mongoDbContext.Db.GetCollection<SemanticDomainTreeNode>("SemanticDomainTree");
+        public IMongoCollection<SemanticDomainFull> FullSemanticDomains => _mongoDbContext.Db.GetCollection<SemanticDomainFull>("SemanticDomains");
     }
 }
diff --git a/Backend/Contexts/SpeakerContext.cs b/Backend/Contexts/SpeakerContext.cs
index f65c3e08c0..e577401afa 100644
--- a/Backend/Contexts/SpeakerContext.cs
+++ b/Backend/Contexts/SpeakerContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,14 +8,13 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class SpeakerContext : ISpeakerContext
     {
-        private readonly IMongoDatabase _db;
+        private readonly IMongoDbContext _mongoDbContext;
 
-        public SpeakerContext(IOptions<Startup.Settings> options)
+        public SpeakerContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<Speaker> Speakers => _db.GetCollection<Speaker>("SpeakersCollection");
+        public IMongoCollection<Speaker> Speakers => _mongoDbContext.Db.GetCollection<Speaker>("SpeakersCollection");
     }
 }
diff --git a/Backend/Contexts/UserContext.cs b/Backend/Contexts/UserContext.cs
index 46122c146c..92778f02d7 100644
--- a/Backend/Contexts/UserContext.cs
+++ b/Backend/Contexts/UserContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,14 +8,12 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class UserContext : IUserContext
     {
-        private readonly IMongoDatabase _db;
-
-        public UserContext(IOptions<Startup.Settings> options)
+        private readonly IMongoDbContext _mongoDbContext;
+        public UserContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<User> Users => _db.GetCollection<User>("UsersCollection");
+        public IMongoCollection<User> Users => _mongoDbContext.Db.GetCollection<User>("UsersCollection");
     }
 }
diff --git a/Backend/Contexts/UserEditContext.cs b/Backend/Contexts/UserEditContext.cs
index 7487d78ec0..d0de83a1a6 100644
--- a/Backend/Contexts/UserEditContext.cs
+++ b/Backend/Contexts/UserEditContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,14 +8,12 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class UserEditContext : IUserEditContext
     {
-        private readonly IMongoDatabase _db;
-
-        public UserEditContext(IOptions<Startup.Settings> options)
+        private readonly IMongoDbContext _mongoDbContext;
+        public UserEditContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<UserEdit> UserEdits => _db.GetCollection<UserEdit>("UserEditsCollection");
+        public IMongoCollection<UserEdit> UserEdits => _mongoDbContext.Db.GetCollection<UserEdit>("UserEditsCollection");
     }
 }
diff --git a/Backend/Contexts/UserRoleContext.cs b/Backend/Contexts/UserRoleContext.cs
index 086c2ffe57..92b7c6506f 100644
--- a/Backend/Contexts/UserRoleContext.cs
+++ b/Backend/Contexts/UserRoleContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,14 +8,12 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class UserRoleContext : IUserRoleContext
     {
-        private readonly IMongoDatabase _db;
-
-        public UserRoleContext(IOptions<Startup.Settings> options)
+        private readonly IMongoDbContext _mongoDbContext;
+        public UserRoleContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<UserRole> UserRoles => _db.GetCollection<UserRole>("UserRolesCollection");
+        public IMongoCollection<UserRole> UserRoles => _mongoDbContext.Db.GetCollection<UserRole>("UserRolesCollection");
     }
 }
diff --git a/Backend/Contexts/WordContext.cs b/Backend/Contexts/WordContext.cs
index 32876c6af2..d8989de00e 100644
--- a/Backend/Contexts/WordContext.cs
+++ b/Backend/Contexts/WordContext.cs
@@ -1,7 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using BackendFramework.Interfaces;
 using BackendFramework.Models;
-using Microsoft.Extensions.Options;
 using MongoDB.Driver;
 
 namespace BackendFramework.Contexts
@@ -9,15 +8,13 @@ namespace BackendFramework.Contexts
     [ExcludeFromCodeCoverage]
     public class WordContext : IWordContext
     {
-        private readonly IMongoDatabase _db;
-
-        public WordContext(IOptions<Startup.Settings> options)
+        private readonly IMongoDbContext _mongoDbContext;
+        public WordContext(IMongoDbContext mongoDbContext)
         {
-            var client = new MongoClient(options.Value.ConnectionString);
-            _db = client.GetDatabase(options.Value.CombineDatabase);
+            _mongoDbContext = mongoDbContext;
         }
 
-        public IMongoCollection<Word> Words => _db.GetCollection<Word>("WordsCollection");
-        public IMongoCollection<Word> Frontier => _db.GetCollection<Word>("FrontierCollection");
+        public IMongoCollection<Word> Words => _mongoDbContext.Db.GetCollection<Word>("WordsCollection");
+        public IMongoCollection<Word> Frontier => _mongoDbContext.Db.GetCollection<Word>("FrontierCollection");
     }
 }
diff --git a/Backend/Interfaces/IMongoDbContext.cs b/Backend/Interfaces/IMongoDbContext.cs
new file mode 100644
index 0000000000..01827db0db
--- /dev/null
+++ b/Backend/Interfaces/IMongoDbContext.cs
@@ -0,0 +1,17 @@
+using System;
+using System.Threading.Tasks;
+using MongoDB.Driver;
+
+namespace BackendFramework.Interfaces;
+
+public interface IMongoDbContext
+{
+    IMongoDatabase Db { get; }
+    Task<IMongoTransaction> BeginTransaction();
+}
+
+public interface IMongoTransaction : IDisposable
+{
+    Task CommitTransactionAsync();
+    Task AbortTransactionAsync();
+}
diff --git a/Backend/Services/MergeService.cs b/Backend/Services/MergeService.cs
index 4e0774a697..bac1396702 100644
--- a/Backend/Services/MergeService.cs
+++ b/Backend/Services/MergeService.cs
@@ -11,14 +11,16 @@ namespace BackendFramework.Services
     /// <summary> More complex functions and application logic for <see cref="Word"/>s </summary>
     public class MergeService : IMergeService
     {
+        private readonly IMongoDbContext _mongoDbContext;
         private readonly IMergeBlacklistRepository _mergeBlacklistRepo;
         private readonly IMergeGraylistRepository _mergeGraylistRepo;
         private readonly IWordRepository _wordRepo;
         private readonly IWordService _wordService;
 
-        public MergeService(IMergeBlacklistRepository mergeBlacklistRepo, IMergeGraylistRepository mergeGraylistRepo,
-            IWordRepository wordRepo, IWordService wordService)
+        public MergeService(IMongoDbContext mongoDbContext, IMergeBlacklistRepository mergeBlacklistRepo,
+            IMergeGraylistRepository mergeGraylistRepo, IWordRepository wordRepo, IWordService wordService)
         {
+            _mongoDbContext = mongoDbContext;
             _mergeBlacklistRepo = mergeBlacklistRepo;
             _mergeGraylistRepo = mergeGraylistRepo;
             _wordRepo = wordRepo;
@@ -75,8 +77,11 @@ public async Task<List<Word>> Merge(string projectId, string userId, List<MergeW
         {
             var keptWords = mergeWordsList.Where(m => !m.DeleteOnly);
             var newWords = keptWords.Select(m => MergePrepParent(projectId, m).Result).ToList();
+            using var transaction = await _mongoDbContext.BeginTransaction();
             await Task.WhenAll(mergeWordsList.Select(m => MergeDeleteChildren(projectId, m)));
-            return await _wordService.Create(userId, newWords);
+            var words = await _wordService.Create(userId, newWords);
+            await transaction.CommitTransactionAsync();
+            return words;
         }
 
         /// <summary> Undo merge </summary>
@@ -92,15 +97,18 @@ public async Task<bool> UndoMerge(string projectId, string userId, MergeUndoIds
                 }
             }
 
+            using var transaction = await _mongoDbContext.BeginTransaction();
             // If children are not restorable, return without any undo.
             if (!await _wordService.RestoreFrontierWords(projectId, ids.ChildIds))
             {
+                // Nothing happens, transaction does not need to commit.
                 return false;
-            };
+            }
             foreach (var parentId in ids.ParentIds)
             {
                 await _wordService.DeleteFrontierWord(projectId, userId, parentId);
             }
+            await transaction.CommitTransactionAsync();
             return true;
         }
 
diff --git a/Backend/Startup.cs b/Backend/Startup.cs
index 708bf293b0..4904a0ef43 100644
--- a/Backend/Startup.cs
+++ b/Backend/Startup.cs
@@ -225,6 +225,9 @@ public void ConfigureServices(IServiceCollection services)
 
             // Register concrete types for dependency injection
 
+            // Mongo context, scoped so it is shared across a single request
+            services.AddScoped<IMongoDbContext, MongoDbContext>();
+
             // Banner types
             services.AddTransient<IBannerContext, BannerContext>();
             services.AddTransient<IBannerRepository, BannerRepository>();
@@ -344,7 +347,8 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IHostApp
 
             // If an admin user has been created via the command line, treat that as a single action and shut the
             // server down so the calling script knows it's been completed successfully or unsuccessfully.
-            var userRepo = app.ApplicationServices.GetService<IUserRepository>();
+            using var startupScope = app.ApplicationServices.CreateAsyncScope();
+            var userRepo = startupScope.ServiceProvider.GetService<IUserRepository>();
             if (userRepo is not null && CreateAdminUser(userRepo))
             {
                 _logger.LogInformation("Stopping application");