diff --git a/src/google/adk/sessions/database_session_service.py b/src/google/adk/sessions/database_session_service.py
index eed1d9eae6..c8e044001a 100644
--- a/src/google/adk/sessions/database_session_service.py
+++ b/src/google/adk/sessions/database_session_service.py
@@ -536,11 +536,7 @@ async def append_event(self, session: Session, event: Event) -> Event:
     is_sqlite = self.db_engine.dialect.name == _SQLITE_DIALECT
     use_row_level_locking = self._supports_row_level_locking()
 
-    state_delta = (
-        event.actions.state_delta
-        if event.actions and event.actions.state_delta
-        else {}
-    )
+    state_delta = event.actions.state_delta if event.actions.state_delta else {}
     state_deltas = _session_util.extract_state_delta(state_delta)
     has_app_delta = bool(state_deltas["app"])
     has_user_delta = bool(state_deltas["user"])
@@ -564,6 +560,18 @@ async def append_event(self, session: Session, event: Event) -> Event:
         if storage_session is None:
           raise ValueError(f"Session {session.id} not found.")
 
+        # Pre-analyze state deltas to determine which scopes actually need
+        # write locks. Most events carry only session-scoped state (or no
+        # state at all), so acquiring FOR UPDATE on app_states / user_states
+        # unnecessarily serializes all concurrent append_event calls.
+        state_deltas = (
+            _session_util.extract_state_delta(event.actions.state_delta)
+            if event.actions.state_delta
+            else None
+        )
+        has_app_delta = bool(state_deltas and state_deltas.get("app"))
+        has_user_delta = bool(state_deltas and state_deltas.get("user"))
+
         storage_app_state = await _select_required_state(
             sql_session=sql_session,
             state_model=schema.StorageAppState,
@@ -622,7 +630,7 @@ async def append_event(self, session: Session, event: Event) -> Event:
           storage_user_state.state = (
               storage_user_state.state | state_deltas["user"]
           )
-        if state_deltas["session"]:
+        if state_deltas and state_deltas["session"]:
           storage_session.state = (
               storage_session.state | state_deltas["session"]
           )