diff --git a/main.go b/main.go
index e98c1c9..de0c572 100644
--- a/main.go
+++ b/main.go
@@ -38,32 +38,28 @@ var (
 // buildCategoryRanger holt alle CIDRs aus Redis, baut einen PCTrie
 // und legt ihn 10 Minuten im Cache ab.
 func buildCategoryRanger(cat string) (cidranger.Ranger, error) {
-	rangerCacheMu.Lock()
-	// Cache-Hit?
+	// --------- 1) Leser-Lock: schneller Cache-Hit
+	rangerCacheMu.RLock()
 	if e, ok := rangerCache[cat]; ok && time.Now().Before(e.expireAt) {
-		rangerCacheMu.Unlock()
+		rangerCacheMu.RUnlock()
 		return e.ranger, nil
 	}
-	rangerCacheMu.Unlock()
+	rangerCacheMu.RUnlock()
 
-	// Redis auslesen
+	// --------- 2) Daten aus Redis ziehen
 	keys, err := rdb.HKeys(ctx, "bl:"+cat).Result()
+	log.Printf("Building ranger for %s - keys: %d", cat, len(keys))
 	if err != nil {
 		return nil, err
 	}
-
 	r := cidranger.NewPCTrieRanger()
 	for _, k := range keys {
-		k = strings.TrimSpace(k)
-		_, ipNet, err := net.ParseCIDR(k)
-		if err != nil {
-			fmt.Printf("⚠️ Ungültiger Redis-Prefix %s: %s\n", cat, k)
-			continue
+		if _, ipNet, err := net.ParseCIDR(strings.TrimSpace(k)); err == nil {
+			_ = r.Insert(cidranger.NewBasicRangerEntry(*ipNet))
 		}
-		_ = r.Insert(cidranger.NewBasicRangerEntry(*ipNet))
 	}
 
-	// Cache aktualisieren
+	// --------- 3) Schreiber-Lock: Cache aktualisieren
 	rangerCacheMu.Lock()
 	rangerCache[cat] = rangerCacheEntry{
 		ranger:   r,
@@ -149,6 +145,8 @@ func main() {
 		return
 	}
 
+	warmUpRangers()
+
 	// Server
 	http.HandleFunc("/", handleGUI)
 	http.HandleFunc("/download/", handleDownload)
@@ -466,6 +464,14 @@ func checkIP(ip netip.Addr, cats []string) ([]string, error) {
 	return matches, nil
 }
 
+func warmUpRangers() {
+	for cat := range blocklistURLs {
+		if _, err := buildCategoryRanger(cat); err != nil {
+			log.Printf("warm-up error for %s: %v", cat, err)
+		}
+	}
+}
+
 // JSON-Helfer
 func writeJSON(w http.ResponseWriter, v any) {
 	w.Header().Set("Content-Type", "application/json")