diff --git a/src/Spd.Manager.Licence/PersonalLicenceAppContract.cs b/src/Spd.Manager.Licence/PersonalLicenceAppContract.cs
index 7ad493dc9..3823499ae 100644
--- a/src/Spd.Manager.Licence/PersonalLicenceAppContract.cs
+++ b/src/Spd.Manager.Licence/PersonalLicenceAppContract.cs
@@ -185,7 +185,7 @@ public record WorkerLicenceCreateResponse
 
 public record LicenceAppDocumentsCache
 {
-    public List<LicAppFileInfo> LicAppFileInfos { get; set; } = new List<LicAppFileInfo>();
+    public List<LicAppFileInfo> Items { get; set; } = new List<LicAppFileInfo>();
 }
 public record LicAppFileInfo
 {
diff --git a/src/Spd.Manager.Licence/PersonalLicenceAppManager.cs b/src/Spd.Manager.Licence/PersonalLicenceAppManager.cs
index ef4395ac9..85053737e 100644
--- a/src/Spd.Manager.Licence/PersonalLicenceAppManager.cs
+++ b/src/Spd.Manager.Licence/PersonalLicenceAppManager.cs
@@ -1,4 +1,4 @@
-using AutoMapper;
+using AutoMapper;
 using MediatR;
 using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.Extensions.Logging;
@@ -166,7 +166,7 @@ public async Task<WorkerLicenceAppUpsertResponse> Handle(AnonymousWorkerLicenceA
         SaveLicenceApplicationCmd saveCmd = _mapper.Map<SaveLicenceApplicationCmd>(request);
         var response = await _licenceAppRepository.SaveLicenceApplicationAsync(saveCmd, ct);
 
-        foreach (LicAppFileInfo licAppFile in appDocCache.LicAppFileInfos)
+        foreach (LicAppFileInfo licAppFile in appDocCache.Items)
         {
             DocumentTypeEnum? docType1 = GetDocumentType1Enum(licAppFile.LicenceDocumentTypeCode);
             DocumentTypeEnum? docType2 = GetDocumentType2Enum(licAppFile.LicenceDocumentTypeCode);
diff --git a/src/Spd.Presentation.Licensing/Controllers/WorkerLicensingController.cs b/src/Spd.Presentation.Licensing/Controllers/WorkerLicensingController.cs
index 78c9be7cf..fdea7d114 100644
--- a/src/Spd.Presentation.Licensing/Controllers/WorkerLicensingController.cs
+++ b/src/Spd.Presentation.Licensing/Controllers/WorkerLicensingController.cs
@@ -36,6 +36,7 @@ public class WorkerLicensingController : SpdControllerBase
         private readonly IMapper _mapper;
         private readonly IRecaptchaVerificationService _recaptchaVerificationService;
         private readonly IDistributedCache _cache;
+        private static Mutex mutex = new(false);
 
         public WorkerLicensingController(ILogger<WorkerLicensingController> logger,
             IPrincipal currentUser,
@@ -286,8 +287,7 @@ public async Task<Guid> UploadLicenceAppFilesAnonymous([FromForm][Required] Lice
 
             CreateDocumentInCacheCommand command = new CreateDocumentInCacheCommand(fileUploadRequest);
             var newFileInfos = await _mediator.Send(command);
-            existingFileInfo.LicAppFileInfos.AddRange(newFileInfos);
-            await _cache.Set($"{keyCode}", existingFileInfo, TimeSpan.FromMinutes(30));
+            await UpdateCache(_cache,keyCode,newFileInfos);
             return keyCode;
         }
 
@@ -314,7 +314,32 @@ public async Task<WorkerLicenceAppUpsertResponse> SubmitSecurityWorkerLicenceApp
 
             AnonymousWorkerLicenceAppSubmitCommand command = new AnonymousWorkerLicenceAppSubmitCommand(jsonRequest, keyCode);
             return await _mediator.Send(command);
+        }
 
+        private static async Task UpdateCache(IDistributedCache cache, Guid keyCode, IEnumerable<LicAppFileInfo> newFileInfos)
+        {
+            try
+            {
+                mutex.WaitOne();
+            }
+            catch (AbandonedMutexException)
+            {
+                return;
+            }
+            try
+            {
+                LicenceAppDocumentsCache existingFileInfo = await cache.Get<LicenceAppDocumentsCache?>(keyCode.ToString());
+                if (existingFileInfo == null)
+                {
+                    throw new ApiException(HttpStatusCode.BadRequest, "invalid key code.");
+                }
+                existingFileInfo.Items.AddRange(newFileInfos);
+                await cache.Set($"{keyCode}", existingFileInfo, TimeSpan.FromMinutes(30));
+            }
+            finally
+            {
+                mutex.ReleaseMutex();
+            }            
         }
         #endregion
     }