diff --git a/src/Server/Controllers/SearchdomainController.cs b/src/Server/Controllers/SearchdomainController.cs
index e0caab6..2acf8dd 100644
--- a/src/Server/Controllers/SearchdomainController.cs
+++ b/src/Server/Controllers/SearchdomainController.cs
@@ -55,6 +55,10 @@ public class SearchdomainController : ControllerBase
     {
         try
         {
+            if (settings.QueryCacheSize <= 0)
+            {
+                settings.QueryCacheSize = 1_000_000; // TODO get rid of this magic number
+            }
             int id = _domainManager.CreateSearchdomain(searchdomain, settings);
             return Ok(new SearchdomainCreateResults(){Id = id, Success = true});
         } catch (Exception)
@@ -255,7 +259,7 @@ public class SearchdomainController : ControllerBase
         }
         (Searchdomain? searchdomain_, int? httpStatusCode, string? message) = SearchdomainHelper.TryGetSearchdomain(_domainManager, searchdomain, _logger);
         if (searchdomain_ is null || httpStatusCode is not null) return StatusCode(httpStatusCode ?? 500, new SearchdomainUpdateResults(){Success = false, Message = message});
-        int elementCount = searchdomain_.queryCache.Count();
+        int elementCount = searchdomain_.queryCache.Count;
         int ElementMaxCount = searchdomain_.settings.QueryCacheSize;
         return Ok(new SearchdomainQueryCacheSizeResults() { SizeBytes = searchdomain_.GetSearchCacheSize(), ElementCount = elementCount, ElementMaxCount = ElementMaxCount, Success = true });
     }
diff --git a/src/Server/Migrations/DatabaseMigrations.cs b/src/Server/Migrations/DatabaseMigrations.cs
index 800396b..e20ada8 100644
--- a/src/Server/Migrations/DatabaseMigrations.cs
+++ b/src/Server/Migrations/DatabaseMigrations.cs
@@ -91,4 +91,10 @@ public static class DatabaseMigrations
         helper.ExecuteSQLNonQuery("ALTER TABLE datapoint ADD COLUMN similaritymethod VARCHAR(512) NULL DEFAULT 'Cosine' AFTER probmethod_embedding", []);
         return 4;
     }
+
+    public static int UpdateFrom4(SQLHelper helper)
+    {
+        helper.ExecuteSQLNonQuery("UPDATE searchdomain SET settings = JSON_SET(settings, '$.QueryCacheSize', 1000000) WHERE JSON_EXTRACT(settings, '$.QueryCacheSize') is NULL;", []); // Set QueryCacheSize to a default of 1000000
+        return 5;
+    }
 }
\ No newline at end of file
diff --git a/src/Server/Views/Home/Searchdomains.cshtml b/src/Server/Views/Home/Searchdomains.cshtml
index f482afe..bbe933b 100644
--- a/src/Server/Views/Home/Searchdomains.cshtml
+++ b/src/Server/Views/Home/Searchdomains.cshtml
@@ -887,12 +887,12 @@
                 var data = [{
                   "name": name,
                   "probmethod": probMethod,
-                  "searchdomain": encodeURIComponent(domains[getSelectedDomainKey()]),
+                  "searchdomain": domains[getSelectedDomainKey()],
                   "attributes": attributes,
                   "datapoints": datapoints
                 }];
                 showToast("@T["Updating entity"]", "primary");
-                fetch(`/Entity`, {
+                fetch(`/Entities`, {
                     method: 'PUT',
                     headers: {
                         'Content-Type': 'application/json'
@@ -1073,6 +1073,8 @@
         let configElementCachereconciliation = document.getElementById('searchdomainConfigCacheReconciliation');
         let configElementCacheSize = document.getElementById('searchdomainConfigQueryCacheSize');
 
+        showThrobber(document.querySelector('#searchdomainConfigQueryCacheSize'), true);
+        showThrobber(document.querySelector('#searchdomainConfigCacheReconciliation'), true);
         let cacheUtilizationPromise = getSearchdomainCacheUtilization(getSelectedDomainKey());
         let databaseUtilizationPromise = getSearchdomainDatabaseUtilization(getSelectedDomainKey());
 
@@ -1114,6 +1116,7 @@
             });
 
         searchdomainConfigPromise.then(searchdomainConfig => {
+            hideThrobber(document.querySelector('#searchdomainConfigCacheReconciliation'), true);
             if (searchdomainConfig != null && searchdomainConfig.Settings != null)
             {
                 configElementCacheSize.value = searchdomainConfig.Settings.QueryCacheSize;
@@ -1126,6 +1129,7 @@
             }
         });
         cacheUtilizationPromise.then(cacheUtilization => {
+            hideThrobber(document.querySelector('#searchdomainConfigQueryCacheSize'), true);
             if (cacheUtilization != null && cacheUtilization.SizeBytes != null)
             {
                 document.querySelector('#cacheUtilization').innerText =
@@ -1309,14 +1313,30 @@
       domainItem.classList.add('list-group-item-danger');
     }
 
-    function showThrobber(element = null) {
+    function showThrobber(element = null, direct = false) {
       if (element == null) element = document;
-      element.querySelector('.spinner').classList.remove('d-none');
+      if (direct) {
+        let spinner = document.createElement('div');
+        spinner.classList.add('spinner');
+        spinner.style.position = "absolute";
+        spinner.style.marginTop = "0.5rem";
+        spinner.style.marginLeft = "0.5rem";
+        element.style.opacity = "0.25";
+        element.parentElement.insertBefore(spinner, element);
+      } else {
+        element.querySelector('.spinner').classList.remove('d-none');
+      }
+
     }
 
-    function hideThrobber(element = null) {
+    function hideThrobber(element = null, direct = false) {
       if (element == null) element = document;
-      element.querySelector('.spinner').classList.add('d-none');
+      if (direct) {
+        element.previousElementSibling.remove()
+        element.style.opacity = "1";
+      } else {
+        element.querySelector('.spinner').classList.add('d-none');
+      }
     }
 
     function showEntityDetails(entity) {
diff --git a/src/Shared/LRUCache.cs b/src/Shared/LRUCache.cs
index 056c5f0..00752be 100644
--- a/src/Shared/LRUCache.cs
+++ b/src/Shared/LRUCache.cs
@@ -1,215 +1,240 @@
 namespace Shared;
 
-
-public class EnumerableLruCache<TKey, TValue> where TKey : notnull
+public sealed class EnumerableLruCache<TKey, TValue> where TKey : notnull
 {
-    private readonly Dictionary<TKey, TValue> _cache;
-    private readonly LinkedList<TKey> _keys = new();
+    private sealed record CacheItem(TKey Key, TValue Value);
+
+    private readonly Dictionary<TKey, LinkedListNode<CacheItem>> _map;
+    private readonly LinkedList<CacheItem> _lruList;
+    private readonly ReaderWriterLockSlim _lock = new();
+
     private int _capacity;
-    private ReaderWriterLockSlim _readerWriterLock;
+
+    public EnumerableLruCache(int capacity)
+    {
+        if (capacity <= 0)
+            throw new ArgumentOutOfRangeException(nameof(capacity));
+
+        _capacity = capacity;
+        _map = new Dictionary<TKey, LinkedListNode<CacheItem>>(capacity);
+        _lruList = new LinkedList<CacheItem>();
+    }
 
     public int Capacity
     {
         get
         {
-            _readerWriterLock.EnterReadLock();
+            _lock.EnterReadLock();
             try
             {
                 return _capacity;
             }
             finally
             {
-                _readerWriterLock.ExitReadLock();
+                _lock.ExitReadLock();
             }
         }
         set
         {
-            _readerWriterLock.EnterWriteLock();
+            ArgumentOutOfRangeException.ThrowIfNegativeOrZero(value);
+
+            _lock.EnterWriteLock();
             try
             {
                 _capacity = value;
-                
-                // Trim cache if new capacity is smaller than current size
-                while (_keys.Count > _capacity)
-                {
-                    TKey last = _keys.Last!.Value;
-                    _keys.RemoveLast();
-                    _cache.Remove(last);
-                }
+                TrimIfNeeded();
             }
             finally
             {
-                _readerWriterLock.ExitWriteLock();
+                _lock.ExitWriteLock();
             }
         }
     }
 
-    public EnumerableLruCache(int capacity)
+    public int Count
     {
-        _readerWriterLock = new();
-        _capacity = capacity;
-        _cache = [];
+        get
+        {
+            _lock.EnterReadLock();
+            try
+            {
+                return _map.Count;
+            }
+            finally
+            {
+                _lock.ExitReadLock();
+            }
+        }
     }
 
     public TValue this[TKey key]
     {
         get
         {
-            _readerWriterLock.EnterReadLock();
+            if (!TryGetValue(key, out var value))
+                throw new KeyNotFoundException();
+
+            return value!;
+        }
+        set => Set(key, value);
+    }
+
+    public bool TryGetValue(TKey key, out TValue? value)
+    {
+        _lock.EnterUpgradeableReadLock();
+        try
+        {
+            if (!_map.TryGetValue(key, out var node))
+            {
+                value = default;
+                return false;
+            }
+
+            value = node.Value.Value;
+
+            // LRU aktualisieren
+            _lock.EnterWriteLock();
             try
             {
-                return _cache[key];
+                _lruList.Remove(node);
+                _lruList.AddFirst(node);
             }
             finally
             {
-                _readerWriterLock.ExitReadLock();
+                _lock.ExitWriteLock();
             }
-        }
-        set
-        {
-            _readerWriterLock.EnterWriteLock();
-            try
-            {
-                if (_cache.TryGetValue(key, out _))
-                {
-                    _keys.Remove(key);
-                }
-                _keys.AddFirst(key);
-                _cache[key] = value;
 
-                if (_keys.Count > _capacity)
-                {
-                    TKey last = _keys.Last!.Value;
-                    _keys.RemoveLast();
-                    _cache.Remove(last);
-                }
-            }
-            finally
-            {
-                _readerWriterLock.ExitWriteLock();
-            }
+            return true;
         }
-    }
-
-    public bool ContainsKey(TKey key)
-    {
-        _readerWriterLock.EnterReadLock();
-        try
+        finally
         {
-            return _cache.ContainsKey(key);
-        } finally
-        {
-            _readerWriterLock.ExitReadLock();
-        }
-    }
-
-    public int Count()
-    {
-        _readerWriterLock.EnterReadLock();
-        try
-        {
-            return _cache.Count;
-        } finally
-        {
-            _readerWriterLock.ExitReadLock();
+            _lock.ExitUpgradeableReadLock();
         }
     }
 
     public void Set(TKey key, TValue value)
     {
-        _readerWriterLock.EnterWriteLock();
+        _lock.EnterWriteLock();
         try
         {
-            if (_cache.TryGetValue(key, out _))
+            if (_map.TryGetValue(key, out var existing))
             {
-                _keys.Remove(key);
+                // Update + nach vorne
+                existing.Value = existing.Value with { Value = value };
+                _lruList.Remove(existing);
+                _lruList.AddFirst(existing);
+                return;
             }
-            _keys.AddFirst(key);
-            _cache[key] = value;
 
-            if (_keys.Count > _capacity)
-            {
-                TKey? last = _keys.Last();
-                _keys.RemoveLast();
-                _cache.Remove(last);
-            }            
-        } finally
+            var item = new CacheItem(key, value);
+            var node = new LinkedListNode<CacheItem>(item);
+
+            _lruList.AddFirst(node);
+            _map[key] = node;
+
+            TrimIfNeeded();
+        }
+        finally
         {
-            _readerWriterLock.ExitWriteLock();
+            _lock.ExitWriteLock();
         }
     }
 
-    public void Remove(TKey key)
+    public bool Remove(TKey key)
     {
-        _readerWriterLock.EnterWriteLock();
+        _lock.EnterWriteLock();
         try
         {
-            _keys.Remove(key);
-            _cache.Remove(key);            
-        } finally
-        {
-            _readerWriterLock.ExitWriteLock();
-        }
-    }
-
-    public bool TryGetValue(TKey key, out TValue? value)
-    {
-        _readerWriterLock.EnterUpgradeableReadLock();
-        try
-        {
-            if (_cache.TryGetValue(key, out value))
-            {
+            if (!_map.TryGetValue(key, out var node))
                 return false;
-            }
-            _readerWriterLock.EnterWriteLock();
-            try
-            {
-                _keys.Remove(key);
-                _keys.AddFirst(key);
-            } finally
-            {
-                _readerWriterLock.ExitWriteLock();
-            }
+
+            _lruList.Remove(node);
+            _map.Remove(key);
             return true;
-        } finally
+        }
+        finally
         {
-            _readerWriterLock.ExitUpgradeableReadLock();
+            _lock.ExitWriteLock();
+        }
+    }
+
+    public bool ContainsKey(TKey key)
+    {
+        _lock.EnterReadLock();
+        try
+        {
+            return _map.ContainsKey(key);
+        }
+        finally
+        {
+            _lock.ExitReadLock();
         }
     }
 
     public Dictionary<TKey, TValue> AsDictionary()
     {
-        _readerWriterLock.EnterReadLock();
+        _lock.EnterReadLock();
         try
         {
-            return new Dictionary<TKey, TValue>(_cache);
+            return _map.Values.ToDictionary(
+                n => n.Value.Key,
+                n => n.Value.Value
+            );
         }
         finally
         {
-            _readerWriterLock.ExitReadLock();
+            _lock.ExitReadLock();
         }
     }
 
     public IEnumerable<KeyValuePair<TKey, TValue>> Items()
     {
-        _readerWriterLock.EnterReadLock();
+        _lock.EnterReadLock();
         try
         {
-            foreach (var key in _keys)
+            foreach (var item in _lruList)
             {
-                if (_cache.TryGetValue(key, out var value))
-                {
-                    yield return new KeyValuePair<TKey, TValue>(key, value);
-                }
+                yield return new KeyValuePair<TKey, TValue>(item.Key, item.Value);
             }
-        } finally
+        }
+        finally
         {
-            _readerWriterLock.ExitReadLock();
+            _lock.ExitReadLock();
         }
     }
 
     public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
     {
-        return Items().GetEnumerator();
+        List<KeyValuePair<TKey, TValue>> snapshot;
+
+        _lock.EnterReadLock();
+        try
+        {
+            snapshot = new List<KeyValuePair<TKey, TValue>>(_map.Count);
+
+            foreach (var item in _lruList)
+            {
+                snapshot.Add(new KeyValuePair<TKey, TValue>(
+                    item.Key,
+                    item.Value
+                ));
+            }
+        }
+        finally
+        {
+            _lock.ExitReadLock();
+        }
+
+        return snapshot.GetEnumerator();
+    }
+
+    private void TrimIfNeeded()
+    {
+        while (_map.Count > _capacity)
+        {
+            var lruNode = _lruList.Last!;
+            _lruList.RemoveLast();
+            _map.Remove(lruNode.Value.Key);
+        }
     }
 }