diff --git a/api/configs/app_config.py b/api/configs/app_config.py
index 4467b84c8666e6..e5edc86bc3d2ee 100644
--- a/api/configs/app_config.py
+++ b/api/configs/app_config.py
@@ -8,6 +8,9 @@
 from configs.packaging import PackagingInfo
 
 
+# TODO: Both `BaseModel` and `BaseSettings` has `model_config` attribute but they are in different types.
+# This inheritance is depends on the order of the classes.
+# It is better to use `BaseSettings` as the base class.
 class DifyConfig(
     # based on pydantic-settings
     BaseSettings,
diff --git a/api/configs/feature/__init__.py b/api/configs/feature/__init__.py
index d8ab749560ecd1..2205b0e169d3b0 100644
--- a/api/configs/feature/__init__.py
+++ b/api/configs/feature/__init__.py
@@ -136,7 +136,7 @@ class HttpConfig(BaseModel):
     def CONSOLE_CORS_ALLOW_ORIGINS(self) -> list[str]:
         return self.inner_CONSOLE_CORS_ALLOW_ORIGINS.split(',')
 
-    inner_WEB_API_CORS_ALLOW_ORIGINS: Optional[str] = Field(
+    inner_WEB_API_CORS_ALLOW_ORIGINS: str = Field(
         description='',
         validation_alias=AliasChoices('WEB_API_CORS_ALLOW_ORIGINS'),
         default='*',
diff --git a/api/configs/middleware/__init__.py b/api/configs/middleware/__init__.py
index b1957efb6b595d..6b3ed1a1009ef5 100644
--- a/api/configs/middleware/__init__.py
+++ b/api/configs/middleware/__init__.py
@@ -144,7 +144,7 @@ class CeleryConfig(DatabaseConfig):
 
     @computed_field
     @property
-    def CELERY_RESULT_BACKEND(self) -> str:
+    def CELERY_RESULT_BACKEND(self) -> str | None:
         return 'db+{}'.format(self.SQLALCHEMY_DATABASE_URI) \
             if self.CELERY_BACKEND == 'database' else self.CELERY_BROKER_URL