diff --git a/mapping_provider/__init__.py b/mapping_provider/__init__.py
index 0e871170c847936329e00e020bb7c23864699209..068b038ea5fd9e8c58bff3a47850f8dd610cd92c 100644
--- a/mapping_provider/__init__.py
+++ b/mapping_provider/__init__.py
@@ -12,7 +12,7 @@ from fastapi import FastAPI
 
 from mapping_provider import config, environment
 from mapping_provider.api import common, map
-from mapping_provider.backends import correlator, inventory, cache
+from mapping_provider.backends import cache, correlator, inventory
 
 logger = logging.getLogger(__name__)
 
diff --git a/mapping_provider/api/map.py b/mapping_provider/api/map.py
index 0fb98c2ebffa91a72af6f3a091ab0ddacb597a59..a022f77c09e7a5db28bf5b168858fcc88c070c67 100644
--- a/mapping_provider/api/map.py
+++ b/mapping_provider/api/map.py
@@ -7,6 +7,7 @@ from pydantic import BaseModel
 
 from mapping_provider import config
 from mapping_provider.backends import services
+
 router = APIRouter()
 
 
diff --git a/mapping_provider/backends/cache.py b/mapping_provider/backends/cache.py
index 879ce54f07dee75dd13e93c10aaeb59a030619df..a4cc5ffc950f5052c5c42070dbba519d93797b8f 100644
--- a/mapping_provider/backends/cache.py
+++ b/mapping_provider/backends/cache.py
@@ -6,10 +6,10 @@ The global variable `cache_dir` is set during FastAPI server startup.
 Could be replaced with a proper caching module in the future, or maybe
 just a simple dict.
 """
-from typing import Any
 import json
-import os
 import logging
+import os
+from typing import Any
 
 logger = logging.getLogger(__name__)
 _cache_dir: str | None = None
@@ -17,7 +17,7 @@ _cache_dir: str | None = None
 
 def init(cache_dir: str) -> None:
     global _cache_dir
-    assert _cache_dir is None, f"cache_dir has already been initialized"
+    assert _cache_dir is None, "cache_dir has already been initialized"
     _cache_dir = cache_dir
     logger.debug(f"set cache directory: {_cache_dir}")
 
@@ -26,7 +26,7 @@ def set(filename: str, data: dict[str, Any]) -> None:
     """
     data must be a JSON-serializable dict.
     """
-    assert _cache_dir is not None, f"cache_dir hasn't been initialized"
+    assert _cache_dir is not None, "cache_dir hasn't been initialized"
     with open(os.path.join(_cache_dir, filename), 'w') as f:
         f.write(json.dumps(data))
     logger.debug(f"wrote cached data: {filename}")
@@ -36,7 +36,7 @@ def get(filename: str) -> Any:
     """
     Loads the cached data, parses it as json & returns the object.
     """
-    assert _cache_dir is not None, f"cache_dir hasn't been initialized"
-    with open(os.path.join(_cache_dir, filename), 'r') as f:
+    assert _cache_dir is not None, "cache_dir hasn't been initialized"
+    with open(os.path.join(_cache_dir, filename)) as f:
         logger.debug(f"reading cached data: {filename}")
         return json.load(f)
diff --git a/mapping_provider/backends/correlator.py b/mapping_provider/backends/correlator.py
index 05d48267dfb0db1cc65e080e0a28340363b6542b..d9ec3b710cd3c03db2bd227d4b735236640f7df6 100644
--- a/mapping_provider/backends/correlator.py
+++ b/mapping_provider/backends/correlator.py
@@ -1,10 +1,8 @@
-import json
 import logging
 import os
 import socket
 import threading
 import time
-from functools import partial
 from typing import TYPE_CHECKING, Any
 
 if TYPE_CHECKING:
@@ -12,8 +10,8 @@ if TYPE_CHECKING:
 
 from pika.exchange_type import ExchangeType
 
-from .rmq.exchange import RabbitMQClient, default_rmq_connection_params
 from . import cache
+from .rmq.exchange import RabbitMQClient, default_rmq_connection_params
 
 logger = logging.getLogger(__name__)
 
diff --git a/mapping_provider/backends/inventory.py b/mapping_provider/backends/inventory.py
index 861dbc65ef38cc70b61738b80017bad66a725eeb..85e1727163b1100b3d13ea6b9cac17faaeecd450 100644
--- a/mapping_provider/backends/inventory.py
+++ b/mapping_provider/backends/inventory.py
@@ -1,9 +1,7 @@
-import json
+import concurrent.futures
 import logging
-import os
 import time
 from threading import Event
-import concurrent.futures
 from typing import Any
 
 import requests
diff --git a/mapping_provider/backends/services.py b/mapping_provider/backends/services.py
index 750c0cc2033d6715ff324a9d613009d0e6f04d35..6abf52336b30368962310ed5391fbf1d7cd9e59e 100644
--- a/mapping_provider/backends/services.py
+++ b/mapping_provider/backends/services.py
@@ -1,6 +1,8 @@
-from pydantic import BaseModel
-from typing import Any, Generator
 import logging
+from collections.abc import Generator
+
+from pydantic import BaseModel
+
 from . import cache, correlator, inventory
 
 logger = logging.getLogger(__name__)
@@ -29,7 +31,7 @@ class ServiceList(BaseModel):
     services: list[Service]
 
 
-def _services(service_type: str | None = None) -> Generator[Service, None, None]:
+def _services(service_type: str | None = None) -> Generator[Service]:
     """
     load the cached backend data and yield map service records
 
@@ -45,7 +47,7 @@ def _services(service_type: str | None = None) -> Generator[Service, None, None]
         logger.exception('not enough data available to build the service list')
         return
 
-    def _get_down_correlator_services() -> Generator[str, None, None]:
+    def _get_down_correlator_services() -> Generator[str]:
         for _e in correlator_state['endpoints']:
             if _e['up']:
                 continue
diff --git a/test/conftest.py b/test/conftest.py
index ee017fe6146c15d098e425afc406feadbf96ab09..60edf83fc32c2e749fea6da7e9efe45a98c336f3 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -7,7 +7,8 @@ import pytest
 from fastapi.testclient import TestClient
 
 from mapping_provider import create_app
-from mapping_provider.backends import cache, inventory, correlator
+from mapping_provider.backends import cache, correlator, inventory
+
 from .common import load_test_data
 
 
diff --git a/test/test_correlator.py b/test/test_correlator.py
index 1f145915955e66be7f29e35312df536679aa7bee..6020af147b0ed665afdcfcdbc9f80302581b0e90 100644
--- a/test/test_correlator.py
+++ b/test/test_correlator.py
@@ -1,5 +1,3 @@
-import json
-import os
 import tempfile
 
 from mapping_provider.backends import cache, correlator
diff --git a/test/test_inventory.py b/test/test_inventory.py
index 26050751ad7002b2488c2cd8cc6ab4c53bed4e00..a68a72bce95127da9f8bfb071e7d14af19bd1ad1 100644
--- a/test/test_inventory.py
+++ b/test/test_inventory.py
@@ -2,7 +2,8 @@ import tempfile
 
 import responses
 
-from mapping_provider.backends import inventory, cache
+from mapping_provider.backends import cache, inventory
+
 from .common import load_test_data