diff --git a/main.py b/main.py
index e6aabc57..a5248f93 100644
--- a/main.py
+++ b/main.py
@@ -333,10 +333,11 @@ def _fetch_folder_rules(folder_id: str):
         try:
             data = _api_get(client, f"{API_BASE}/{profile_id}/rules/{folder_id}").json()
             folder_rules = data.get("body", {}).get("rules", [])
-            with all_rules_lock:
-                for rule in folder_rules:
-                    if rule.get("PK"):
-                        all_rules.add(rule["PK"])
+            # Optimization: Extract PKs locally to minimize lock contention
+            local_pks = {rule["PK"] for rule in folder_rules if rule.get("PK")}
+            if local_pks:
+                with all_rules_lock:
+                    all_rules.update(local_pks)
         except httpx.HTTPError:
             pass
         except Exception as e: