diff --git a/flake.nix b/flake.nix
index ea4383f..76e570c 100644
--- a/flake.nix
+++ b/flake.nix
@@ -61,17 +61,17 @@
           in ''
             ${
               if builtins.elem "pytest" dev && !skipCheck
-              then "pytest src tests"
+              then "pytest tests"
               else ""
             }
             ${
               if builtins.elem "mypy" dev && !skipCheck
-              then "mypy src tests"
+              then "mypy src"
               else ""
             }
             ${
               if builtins.elem "pylint" dev && !skipCheck
-              then "pylint src tests"
+              then "pylint src"
               else ""
             }
           '';
diff --git a/pyproject.toml b/pyproject.toml
index 9635067..8e161b8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,7 +31,7 @@ where = ["src"]
 testdata = ["py.typed"]
 
 [tool.autopep8]
-max_line_length = 150
+max_line_length = 175
 
 [tool.pylint.'MESSAGES CONTROL']
 disable = [
diff --git a/src/testdata/logger/logger.py b/src/testdata/logger/logger.py
index 8c6b9a9..9e64f19 100644
--- a/src/testdata/logger/logger.py
+++ b/src/testdata/logger/logger.py
@@ -132,7 +132,7 @@ def generate_log_config(log_path: str | None = None) -> dict:
                 'class': logging.handlers.RotatingFileHandler,
                 'level': 'DEBUG',
                 'formatter': 'json',
-                'filename': 'log.jsonl',
+                'filename': log_path,
                 'maxBytes': 1024 * 1024 * 10,  # 10 MiB
                 'backupCount': 3
         }} if log_path is not None else {}),
diff --git a/src/testdata/main.py b/src/testdata/main.py
index daa378d..7861a20 100644
--- a/src/testdata/main.py
+++ b/src/testdata/main.py
@@ -1,12 +1,17 @@
 import sys
 import argparse
 import asyncio
+import shutil
 
 from .testdata import Testdata
 
 def parse_args(args: list[str]):
-    parser = argparse.ArgumentParser()
-    parser.add_argument('-c', '--config', type=argparse.FileType('r'), default='./config.json', help='Path to config file in JSON format.')
+    def formatter(prog):
+        return argparse.ArgumentDefaultsHelpFormatter(prog, max_help_position=shutil.get_terminal_size().columns)
+
+    parser = argparse.ArgumentParser(formatter_class=formatter)
+
+    parser.add_argument('-c', '--config', type=argparse.FileType('r'), default='./config.json', help='Path to config file in JSON format.', )
     parser.add_argument('-l', '--listen', type=str, default='0.0.0.0', help='IP on which to listen.')
     parser.add_argument('-p', '--port', type=int, default='8080', help='Port on which to serve the webserver.')
 
diff --git a/src/testdata/testdata.py b/src/testdata/testdata.py
index 09c001d..8413d23 100644
--- a/src/testdata/testdata.py
+++ b/src/testdata/testdata.py
@@ -4,6 +4,8 @@ import asyncio
 import inspect
 import functools
 import random
+import importlib.metadata
+from datetime import datetime
 
 import uvicorn
 from typing_extensions import Annotated
@@ -53,7 +55,7 @@ class Testdata:
 
     _config: Config
     _api: FastAPI
-    _state: dict[str, int]
+    _state: dict
     _logger: logger.Logger
 
     def __init__(self, config: Config):
@@ -62,7 +64,10 @@ class Testdata:
         self._api = self._setup_api()
 
         # Store internal state
-        self._state = {'data-used': 0}
+        self._state = {
+            'version': importlib.metadata.version('testdata'),  # For future compatibility
+            'data-used': {f'{(today := datetime.today()).year}-{today.month:02}': 0}  # math each months data usage
+        }
 
     def _setup_api(self) -> FastAPI:
         api = FastAPI(docs_url='/', redoc_url=None)
@@ -162,12 +167,15 @@ class Testdata:
                 raise MaxSizePerRequestError
 
             # update internal state
-            if self._config.max_data < self._state['data-used'] + size:
+            current_date = f'{(today := datetime.today()).year}-{today.month:02}'
+            if current_date not in self._state['data-used']:
+                self._state['data-used'][current_date] = 0
+            if self._config.max_data < self._state['data-used'][current_date] + size:
                 raise HTTPException(
                     status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                     detail='Service not available.'
                 )
-            self._state['data-used'] += size
+            self._state['data-used'][current_date] += size
 
             self._logger.debug('Successfully processed request.', extra=extra)
             return StreamingResponse(
@@ -209,7 +217,7 @@ class Testdata:
 
             while True:
                 file.seek(0)
-                json.dump(self._state, file)
+                json.dump(self._state, file, indent=2)
                 file.truncate()
                 await asyncio.sleep(self._config.database_update_interval)
 
diff --git a/tests/test_testdata.py b/tests/test_testdata.py
index 4ec3745..cb38bd8 100644
--- a/tests/test_testdata.py
+++ b/tests/test_testdata.py
@@ -102,15 +102,29 @@ def test_invalid_api_key(_server):
     'database-update-interval': 0.1
 })], indirect=['_server'])
 def test_check_database_update(_server):
+    import importlib.metadata
+    from datetime import datetime
+
     database = _server
 
     with open(database, 'r', encoding='utf-8') as file:
         file.seek(0)
-        assert json.load(file) == {'data-used': 0}
+        today = datetime.today()
+        assert json.load(file) == {
+            'version': importlib.metadata.version('testdata'),
+            'data-used': {
+                f'{today.year}-{today.month:02}': 0
+            }
+        }
 
         response = requests.get(f'{PROTOCOL}://{HOST}:{PORT}/zeros?api_key=one&size=100', timeout=TIMEOUT)
         assert response.status_code == 200
 
         time.sleep(0.1)
         file.seek(0)
-        assert json.load(file) == {'data-used': 100}
+        assert json.load(file) == {
+            'version': importlib.metadata.version('testdata'),
+            'data-used': {
+                f'{today.year}-{today.month:02}': 100
+            }
+        }