diff --git a/src/strawchemy/sqlalchemy/repository/_base.py b/src/strawchemy/sqlalchemy/repository/_base.py
index d216558..c7a52e7 100644
--- a/src/strawchemy/sqlalchemy/repository/_base.py
+++ b/src/strawchemy/sqlalchemy/repository/_base.py
@@ -30,6 +30,8 @@
     from strawchemy.strawberry.typing import QueryNodeType
     from strawchemy.typing import SupportedDialect
 
+    RowLike: TypeAlias = "Row[Any] | NamedTuple"
+
 
 __all__ = ("InsertOrUpdate", "RowLike", "SQLAlchemyGraphQLRepository")
 
@@ -228,22 +230,42 @@ def _m2m_values(
         self, model: DeclarativeBase, parent: Union[RowLike, DeclarativeBase], relationship: RelationshipProperty[Any]
     ) -> dict[str, Any]:
         assert relationship.local_remote_pairs
-        return {
-            remote.key: getattr(model, local.key) if local.table is model.__table__ else getattr(parent, local.key)
-            for local, remote in relationship.local_remote_pairs
-            if local.key and remote.key
-        }
+
+        # Local optimization: avoid attribute access twice per key by pulling out __table__ and .__dict__
+        model_table = model.__table__
+        model_dict = model.__dict__
+        parent_dict = parent.__dict__ if hasattr(parent, "__dict__") else None
+
+        result = {}
+        for local, remote in relationship.local_remote_pairs:
+            if local.key and remote.key:
+                # Use __dict__ for direct attribute access if possible, avoids getattr descriptor resolution
+                if local.table is model_table:
+                    value = model_dict[local.key]
+                else:
+                    value = (
+                        parent_dict[local.key]
+                        if parent_dict is not None and local.key in parent_dict
+                        else getattr(parent, local.key)
+                    )
+                result[remote.key] = value
+        return result
 
     def _update_values(
         self, model: DeclarativeBase, parent: Union[RowLike, DeclarativeBase], relationship: RelationshipProperty[Any]
     ) -> dict[str, Any]:
         assert relationship.local_remote_pairs
         if relationship.secondary is None:
-            return {column.key: getattr(model, column.key) for column in model.__mapper__.primary_key if column.key} | {
-                remote.key: getattr(parent, local.key)
-                for local, remote in relationship.local_remote_pairs
-                if local.key and remote.key
-            }
+            # Local optimization: use dict update instead of dict union for performance,
+            # and re-use dicts for primary_key and remote mapping.
+            d = {}
+            for column in model.__mapper__.primary_key:
+                if column.key:
+                    d[column.key] = getattr(model, column.key)
+            for local, remote in relationship.local_remote_pairs:
+                if local.key and remote.key:
+                    d[remote.key] = getattr(parent, local.key)
+            return d
         return self._m2m_values(model, parent, relationship)
 
     def _to_one_nested_create_params(self, level: LevelInput) -> QueryParams: