diff --git a/F4SD-Cockpit-ServerCore/DataHistoryCollectorM42Wpm.cs b/F4SD-Cockpit-ServerCore/DataHistoryCollectorM42Wpm.cs
index 9c7244a..44c7a32 100644
--- a/F4SD-Cockpit-ServerCore/DataHistoryCollectorM42Wpm.cs
+++ b/F4SD-Cockpit-ServerCore/DataHistoryCollectorM42Wpm.cs
@@ -99,6 +99,7 @@ namespace C4IT.DataHistoryProvider
         private Dictionary<WebClientCacheIndex, WebClientCacheEntry> UserWebClientCache = new Dictionary<WebClientCacheIndex, WebClientCacheEntry>();
 
         private readonly object _ticketOverviewCacheLock = new object();
+        private readonly Dictionary<Guid, Guid> _ticketOverviewUserIds = new Dictionary<Guid, Guid>();
 
         [Obsolete]
         private readonly Dictionary<string, TicketOverviewCountCacheEntry> _ticketOverviewPersonalCache = new Dictionary<string, TicketOverviewCountCacheEntry>(StringComparer.OrdinalIgnoreCase);
@@ -1212,8 +1213,60 @@ namespace C4IT.DataHistoryProvider
                 urlBuilder.Append("&queues=").Append(encodedQueues);
         }
 
+        private void CacheTicketOverviewUserId(Guid cockpitUserId, Guid matrix42UserId)
+        {
+            if (cockpitUserId == Guid.Empty || matrix42UserId == Guid.Empty)
+                return;
+
+            lock (_ticketOverviewCacheLock)
+                _ticketOverviewUserIds[cockpitUserId] = matrix42UserId;
+        }
+
+        private async Task<Guid> ResolveTicketOverviewUserIdAsync(
+            cF4sdWebRequestInfo requestInfo,
+            int logDeep,
+            CancellationToken token)
+        {
+            var cockpitUserId = requestInfo?.userInfo?.Id ?? Guid.Empty;
+            if (cockpitUserId == Guid.Empty)
+                return Guid.Empty;
+
+            lock (_ticketOverviewCacheLock)
+            {
+                if (_ticketOverviewUserIds.TryGetValue(cockpitUserId, out var cachedUserId))
+                    return cachedUserId;
+            }
+
+            var sid = requestInfo?.userInfo?.AdSid;
+            if (!string.IsNullOrWhiteSpace(sid))
+            {
+                var userInfo = await GetM42UserInfoAsync(sid, token);
+                var matrix42UserId = userInfo?.User?.Id ?? Guid.Empty;
+                if (matrix42UserId != Guid.Empty)
+                {
+                    CacheTicketOverviewUserId(cockpitUserId, matrix42UserId);
+                    return matrix42UserId;
+                }
+            }
+
+            var userWebClient = await GetUserWebClient(requestInfo, logDeep + 1, token);
+            if (userWebClient != null)
+            {
+                var userInfo = await userWebClient.GetUserInfoAsync(token);
+                var matrix42UserId = userInfo?.User?.Id ?? Guid.Empty;
+                if (matrix42UserId != Guid.Empty)
+                {
+                    CacheTicketOverviewUserId(cockpitUserId, matrix42UserId);
+                    return matrix42UserId;
+                }
+            }
+
+            LogEntry($"Could not resolve a Matrix42 user ID for authenticated F4SD user {cockpitUserId}. Ticket overview request was skipped.", LogLevels.Warning);
+            return Guid.Empty;
+        }
+
         private async Task<Dictionary<string, int>> FetchTicketOverviewCountsAsync(
-            string sid,
+            Guid userId,
             string scope,
             IReadOnlyCollection<string> requestedKeys,
             cF4sdWebRequestInfo requestInfo,
@@ -1224,27 +1277,12 @@ namespace C4IT.DataHistoryProvider
                 var wc = await GetWebClient(requestInfo, token);
                 var request = new cTicketOverviewFilterRequest
                 {
-                    Sid = sid,
+                    UserId = userId,
                     Scope = scope,
                     Keys = requestedKeys?.ToList() ?? new List<string>(),
                     Filters = GetTicketFilters()
                 };
                 var res = await PostJsonAsync(wc, constUrlGetTicketOverviewCountsV2, request, token);
-                if (res?.StatusCode == HttpStatusCode.NotFound)
-                {
-                    if (!TryGetLegacyQueueFilter(out var queueOption, out var encodedQueues))
-                    {
-                        LogEntry("The ticket filter policy requires the v2 overview API; legacy fallback was rejected (fail closed).", LogLevels.Warning);
-                        return new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
-                    }
-                    var urlBuilder = new StringBuilder(constUrlGetTicketOverviewCounts);
-                    urlBuilder.Append("?sid=").Append(HttpUtility.UrlEncode(sid));
-                    urlBuilder.Append("&scope=").Append(HttpUtility.UrlEncode(scope ?? string.Empty));
-                    if (requestedKeys != null && requestedKeys.Count > 0)
-                        urlBuilder.Append("&keys=").Append(HttpUtility.UrlEncode(string.Join(",", requestedKeys)));
-                    AppendQueueFilterQuery(urlBuilder, queueOption, encodedQueues);
-                    res = await wc.HttpEnh.GetAsync(urlBuilder.ToString(), token);
-                }
                 if (token.IsCancellationRequested)
                     return new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
 
@@ -1308,8 +1346,8 @@ namespace C4IT.DataHistoryProvider
                 if (!await CheckOnline())
                     return new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
 
-                var sid = requestInfo?.userInfo?.AdSid;
-                if (string.IsNullOrWhiteSpace(sid))
+                var userId = await ResolveTicketOverviewUserIdAsync(requestInfo, LogDeep, Token);
+                if (userId == Guid.Empty)
                     return new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
 
                 var normalizedKeys = (keys ?? Enumerable.Empty<string>())
@@ -1317,7 +1355,7 @@ namespace C4IT.DataHistoryProvider
                     .Distinct(StringComparer.OrdinalIgnoreCase)
                     .ToList();
                 var scope = useRoleScope ? "role" : "personal";
-                return await FetchTicketOverviewCountsAsync(sid, scope, normalizedKeys, requestInfo, Token);
+                return await FetchTicketOverviewCountsAsync(userId, scope, normalizedKeys, requestInfo, Token);
             }
             catch (Exception E)
             {
@@ -1346,36 +1384,21 @@ namespace C4IT.DataHistoryProvider
                 if (string.IsNullOrWhiteSpace(key))
                     return new List<cF4sdApiSearchResultRelation>();
 
-                var sid = requestInfo?.userInfo?.AdSid;
-                if (string.IsNullOrWhiteSpace(sid))
+                var userId = await ResolveTicketOverviewUserIdAsync(requestInfo, LogDeep, Token);
+                if (userId == Guid.Empty)
                     return new List<cF4sdApiSearchResultRelation>();
 
                 var scope = useRoleScope ? "role" : "personal";
                 var wc = await GetWebClient(requestInfo, Token);
                 var request = new cTicketOverviewFilterRequest
                 {
-                    Sid = sid,
+                    UserId = userId,
                     Scope = scope,
                     Key = key,
                     Count = Math.Max(0, count),
                     Filters = GetTicketFilters()
                 };
                 var res = await PostJsonAsync(wc, constUrlGetTicketOverviewRelationsV2, request, Token);
-                if (res?.StatusCode == HttpStatusCode.NotFound)
-                {
-                    if (!TryGetLegacyQueueFilter(out var queueOption, out var encodedQueues))
-                    {
-                        LogEntry("The ticket filter policy requires the v2 relation API; legacy fallback was rejected (fail closed).", LogLevels.Warning);
-                        return new List<cF4sdApiSearchResultRelation>();
-                    }
-                    var urlBuilder = new StringBuilder(constUrlGetTicketOverviewRelations);
-                    urlBuilder.Append("?sid=").Append(HttpUtility.UrlEncode(sid));
-                    urlBuilder.Append("&scope=").Append(HttpUtility.UrlEncode(scope));
-                    urlBuilder.Append("&key=").Append(HttpUtility.UrlEncode(key));
-                    urlBuilder.Append("&count=").Append(Math.Max(0, count));
-                    AppendQueueFilterQuery(urlBuilder, queueOption, encodedQueues);
-                    res = await wc.HttpEnh.GetAsync(urlBuilder.ToString(), Token);
-                }
                 if (Token.IsCancellationRequested)
                     return new List<cF4sdApiSearchResultRelation>();
 
@@ -2357,6 +2380,8 @@ namespace C4IT.DataHistoryProvider
                 if (Token.IsCancellationRequested)
                     return;
 
+                CacheTicketOverviewUserId(userInfo.Id, _M42UserInfo?.User?.Id ?? Guid.Empty);
+
                 // if yes, set M42 for an addidional automatic logon possibility
                 if (_M42UserInfo?.User != null)
                 {
@@ -2431,6 +2456,8 @@ namespace C4IT.DataHistoryProvider
                     // get the role memberships relatet to the M42 roles
                     if (m42UserInfo?.User?.Id != null)
                     {
+                        CacheTicketOverviewUserId(userInfo.Id, (Guid)m42UserInfo.User.Id);
+
                         var _F4SDRoles = await GetF4SDRoles((Guid)m42UserInfo.User.Id, Token);
 
                         if (_F4SDRoles?.Count > 0)