diff --git a/fastapi_traffic/core/config.py b/fastapi_traffic/core/config.py
index 665a443..a538fc2 100644
--- a/fastapi_traffic/core/config.py
+++ b/fastapi_traffic/core/config.py
@@ -2,8 +2,9 @@
 
 from __future__ import annotations
 
+from collections.abc import Callable
 from dataclasses import dataclass, field
-from typing import TYPE_CHECKING, Any, Callable
+from typing import TYPE_CHECKING, Any
 
 from fastapi_traffic.core.algorithms import Algorithm
 
diff --git a/fastapi_traffic/core/decorator.py b/fastapi_traffic/core/decorator.py
index 5148405..4f99d3c 100644
--- a/fastapi_traffic/core/decorator.py
+++ b/fastapi_traffic/core/decorator.py
@@ -3,19 +3,26 @@
 from __future__ import annotations
 
 import functools
-from typing import TYPE_CHECKING, Any, Callable, TypeVar, overload
+from collections.abc import Callable
+from typing import TYPE_CHECKING, Any, TypeVar, overload
 
 from fastapi_traffic.core.algorithms import Algorithm
-from fastapi_traffic.core.config import KeyExtractor, RateLimitConfig, default_key_extractor
+from fastapi_traffic.core.config import (
+    KeyExtractor,
+    RateLimitConfig,
+    default_key_extractor,
+)
 from fastapi_traffic.core.limiter import get_limiter
-from fastapi_traffic.exceptions import RateLimitExceeded
 
 if TYPE_CHECKING:
     from starlette.requests import Request
     from starlette.responses import Response
 
+    from fastapi_traffic.exceptions import RateLimitExceeded
+
 F = TypeVar("F", bound=Callable[..., Any])
 
+# Note: Config loader from secrets .env
 
 @overload
 def rate_limit(
diff --git a/fastapi_traffic/middleware.py b/fastapi_traffic/middleware.py
index 8583d05..d734324 100644
--- a/fastapi_traffic/middleware.py
+++ b/fastapi_traffic/middleware.py
@@ -3,18 +3,24 @@
 from __future__ import annotations
 
 import logging
-from typing import TYPE_CHECKING, Awaitable, Callable
+from typing import TYPE_CHECKING
 
 from starlette.middleware.base import BaseHTTPMiddleware
 from starlette.responses import JSONResponse
 
 from fastapi_traffic.backends.memory import MemoryBackend
 from fastapi_traffic.core.algorithms import Algorithm
-from fastapi_traffic.core.config import GlobalConfig, RateLimitConfig, default_key_extractor
+from fastapi_traffic.core.config import (
+    GlobalConfig,
+    RateLimitConfig,
+    default_key_extractor,
+)
 from fastapi_traffic.core.limiter import RateLimiter
 from fastapi_traffic.exceptions import RateLimitExceeded
 
 if TYPE_CHECKING:
+    from collections.abc import Awaitable, Callable
+
     from starlette.requests import Request
     from starlette.responses import Response
     from starlette.types import ASGIApp