diff --git a/backend/src/Squidex.Infrastructure/Assets/ImageSharp/ImageSharpAssetThumbnailGenerator.cs b/backend/src/Squidex.Infrastructure/Assets/ImageSharp/ImageSharpAssetThumbnailGenerator.cs
index 2c44d9340..cfcb8e9ca 100644
--- a/backend/src/Squidex.Infrastructure/Assets/ImageSharp/ImageSharpAssetThumbnailGenerator.cs
+++ b/backend/src/Squidex.Infrastructure/Assets/ImageSharp/ImageSharpAssetThumbnailGenerator.cs
@@ -7,6 +7,7 @@
 
 using System;
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp;
 using SixLabors.ImageSharp.Formats.Jpeg;
@@ -19,76 +20,89 @@ namespace Squidex.Infrastructure.Assets.ImageSharp
 {
     public sealed class ImageSharpAssetThumbnailGenerator : IAssetThumbnailGenerator
     {
-        public Task CreateThumbnailAsync(Stream source, Stream destination, ResizeOptions options)
+        private readonly SemaphoreSlim semaphoreSlim = new SemaphoreSlim(Math.Max(Environment.ProcessorCount / 4, 1));
+
+        public async Task CreateThumbnailAsync(Stream source, Stream destination, ResizeOptions options)
         {
+            Guard.NotNull(source, nameof(source));
+            Guard.NotNull(destination, nameof(destination));
             Guard.NotNull(options, nameof(options));
 
             if (!options.IsValid)
             {
                 source.CopyTo(destination);
 
-                return Task.CompletedTask;
+                return;
             }
 
             var w = options.Width ?? 0;
             var h = options.Height ?? 0;
 
-            using (var image = Image.Load(source, out var format))
-            {
-                var encoder = Configuration.Default.ImageFormatsManager.FindEncoder(format);
-
-                if (encoder == null)
-                {
-                    throw new NotSupportedException();
-                }
-
-                if (options.Quality.HasValue && (encoder is JpegEncoder || !options.KeepFormat))
-                {
-                    encoder = new JpegEncoder { Quality = options.Quality.Value };
-                }
+            await semaphoreSlim.WaitAsync();
 
-                image.Mutate(x => x.AutoOrient());
-
-                if (w > 0 || h > 0)
+            try
+            {
+                using (var image = Image.Load(source, out var format))
                 {
-                    var isCropUpsize = options.Mode == ResizeMode.CropUpsize;
+                    var encoder = Configuration.Default.ImageFormatsManager.FindEncoder(format);
 
-                    if (!Enum.TryParse<ISResizeMode>(options.Mode.ToString(), true, out var resizeMode))
+                    if (encoder == null)
                     {
-                        resizeMode = ISResizeMode.Max;
+                        throw new NotSupportedException();
                     }
 
-                    if (isCropUpsize)
+                    if (options.Quality.HasValue && (encoder is JpegEncoder || !options.KeepFormat))
                     {
-                        resizeMode = ISResizeMode.Crop;
+                        encoder = new JpegEncoder { Quality = options.Quality.Value };
                     }
 
-                    if (w >= image.Width && h >= image.Height && resizeMode == ISResizeMode.Crop && !isCropUpsize)
-                    {
-                        resizeMode = ISResizeMode.BoxPad;
-                    }
-
-                    var resizeOptions = new ISResizeOptions { Size = new Size(w, h), Mode = resizeMode };
+                    image.Mutate(x => x.AutoOrient());
 
-                    if (options.FocusX.HasValue && options.FocusY.HasValue)
+                    if (w > 0 || h > 0)
                     {
-                        resizeOptions.CenterCoordinates = new PointF(
-                            +(options.FocusX.Value / 2f) + 0.5f,
-                            -(options.FocusY.Value / 2f) + 0.5f
-                        );
+                        var isCropUpsize = options.Mode == ResizeMode.CropUpsize;
+
+                        if (!Enum.TryParse<ISResizeMode>(options.Mode.ToString(), true, out var resizeMode))
+                        {
+                            resizeMode = ISResizeMode.Max;
+                        }
+
+                        if (isCropUpsize)
+                        {
+                            resizeMode = ISResizeMode.Crop;
+                        }
+
+                        if (w >= image.Width && h >= image.Height && resizeMode == ISResizeMode.Crop && !isCropUpsize)
+                        {
+                            resizeMode = ISResizeMode.BoxPad;
+                        }
+
+                        var resizeOptions = new ISResizeOptions { Size = new Size(w, h), Mode = resizeMode };
+
+                        if (options.FocusX.HasValue && options.FocusY.HasValue)
+                        {
+                            resizeOptions.CenterCoordinates = new PointF(
+                                +(options.FocusX.Value / 2f) + 0.5f,
+                                -(options.FocusY.Value / 2f) + 0.5f
+                            );
+                        }
+
+                        image.Mutate(x => x.Resize(resizeOptions));
                     }
 
-                    image.Mutate(x => x.Resize(resizeOptions));
+                    image.Save(destination, encoder);
                 }
-
-                image.Save(destination, encoder);
             }
-
-            return Task.CompletedTask;
+            finally
+            {
+                semaphoreSlim.Release();
+            }
         }
 
         public Task<ImageInfo?> GetImageInfoAsync(Stream source)
         {
+            Guard.NotNull(source, nameof(source));
+
             ImageInfo? result = null;
 
             try
@@ -108,22 +122,34 @@ namespace Squidex.Infrastructure.Assets.ImageSharp
             return Task.FromResult(result);
         }
 
-        public Task<ImageInfo> FixOrientationAsync(Stream source, Stream destination)
+        public async Task<ImageInfo> FixOrientationAsync(Stream source, Stream destination)
         {
-            using (var image = Image.Load(source, out var format))
-            {
-                var encoder = Configuration.Default.ImageFormatsManager.FindEncoder(format);
+            Guard.NotNull(source, nameof(source));
+            Guard.NotNull(destination, nameof(destination));
+
+            await semaphoreSlim.WaitAsync();
 
-                if (encoder == null)
+            try
+            {
+                using (var image = Image.Load(source, out var format))
                 {
-                    throw new NotSupportedException();
-                }
+                    var encoder = Configuration.Default.ImageFormatsManager.FindEncoder(format);
+
+                    if (encoder == null)
+                    {
+                        throw new NotSupportedException();
+                    }
 
-                image.Mutate(x => x.AutoOrient());
+                    image.Mutate(x => x.AutoOrient());
 
-                image.Save(destination, encoder);
+                    image.Save(destination, encoder);
 
-                return Task.FromResult(GetImageInfo(image));
+                    return GetImageInfo(image);
+                }
+            }
+            finally
+            {
+                semaphoreSlim.Release();
             }
         }