diff --git a/store/models.py b/store/models.py
index ee3af58..f69c5c0 100644
--- a/store/models.py
+++ b/store/models.py
@@ -512,6 +512,7 @@ class Checklist(models.Model):
         # Default commission
         commission = GlobalSettings.load().commission_rub
 
+        # For big orders there is an additional commission
         if self.price_rub > 150_000:
             commission = max(commission, self.price_rub * Decimal(settings.COMMISSION_OVER_150K))
 
diff --git a/store/urls.py b/store/urls.py
index 16a06e2..d63cced 100644
--- a/store/urls.py
+++ b/store/urls.py
@@ -12,11 +12,9 @@ router.register(r'cdek', views.CDEKAPI, basename='cdek')
 router.register(r'gifts', views.GiftAPI, basename='gifts')
 router.register(r'poizon', views.PoizonAPI, basename='poizon')
 router.register(r'promo', views.PromoCodeAPI, basename='promo')
+router.register(r'category', views.CategoryAPI, basename='category')
 
 urlpatterns = [
-    path("category/", views.CategoryAPI.as_view()),
-    path("category/<int:id>", views.CategoryAPI.as_view()),
-
     path("payment/", views.PaymentMethodsAPI.as_view()),
     path("settings/", views.GlobalSettingsAPI.as_view()),
 
diff --git a/store/views.py b/store/views.py
index 8e2d3f0..88996a7 100644
--- a/store/views.py
+++ b/store/views.py
@@ -3,7 +3,7 @@ from datetime import timedelta
 
 import requests
 from django.conf import settings
-from django.db.models import F, Count, Sum, OuterRef, Subquery
+from django.db.models import F, Count, Sum
 from django_filters.rest_framework import DjangoFilterBackend
 from rest_framework import generics, permissions, mixins, status, viewsets
 from rest_framework.decorators import action
@@ -114,21 +114,16 @@ class ChecklistAPI(viewsets.ModelViewSet):
         return obj
 
 
-class CategoryAPI(mixins.ListModelMixin, mixins.UpdateModelMixin, generics.GenericAPIView):
+class CategoryAPI(mixins.ListModelMixin, mixins.RetrieveModelMixin, mixins.UpdateModelMixin, viewsets.GenericViewSet):
     serializer_class = CategorySerializer
     permission_classes = [IsManager | ReadOnly]
     lookup_field = 'id'
+    queryset = Category.objects.all()
 
-    def get_queryset(self):
-        return Category.objects.all()
-
-    def get(self, request, *args, **kwargs):
+    def list(self, request, *args, **kwargs):
         categories_qs = Category.objects.root_nodes()
         return Response(CategoryFullSerializer(categories_qs, many=True).data)
 
-    def patch(self, request, *args, **kwargs):
-        return self.partial_update(request, *args, **kwargs)
-
 
 class GlobalSettingsAPI(generics.RetrieveUpdateAPIView):
     serializer_class = GlobalSettingsSerializer
@@ -145,12 +140,11 @@ class GlobalSettingsAPI(generics.RetrieveUpdateAPIView):
         return GlobalSettings.load()
 
 
+# TODO: update to GenericViewSet
 class PaymentMethodsAPI(generics.GenericAPIView):
     serializer_class = PaymentMethodSerializer
     permission_classes = [IsManager | ReadOnly]
-
-    def get_queryset(self):
-        return PaymentMethod.objects.all()
+    queryset = PaymentMethod.objects.all()
 
     def get(self, request, *args, **kwargs):
         qs = self.get_queryset()
diff --git a/utils/exceptions.py b/utils/exceptions.py
index 7701c81..13ccf4e 100644
--- a/utils/exceptions.py
+++ b/utils/exceptions.py
@@ -10,3 +10,6 @@ class CRMException(APIException):
             detail = self.default_detail
 
         self.detail = {'error': detail}
+
+
+# TODO: exceptions with a same template: ok / error_code / error_message