diff --git a/dibbler/models/Transaction.py b/dibbler/models/Transaction.py
index e446a38..bb76b44 100644
--- a/dibbler/models/Transaction.py
+++ b/dibbler/models/Transaction.py
@@ -64,6 +64,7 @@ assert all(x <= _DYNAMIC_FIELDS for x in _EXPECTED_FIELDS.values()), (
     "All expected fields must be part of _DYNAMIC_FIELDS."
 )
 
+# TODO: ensure that the transaction types are not prefixed with 'TransactionType.' in the database
 
 def _transaction_type_field_constraints(
     transaction_type: TransactionType,
diff --git a/dibbler/models/User.py b/dibbler/models/User.py
index d359d13..7f7d01c 100644
--- a/dibbler/models/User.py
+++ b/dibbler/models/User.py
@@ -47,6 +47,7 @@ class User(Base):
     #     return self.card == "11122233"
 
     # TODO: move to 'queries'
+    # TODO: allow filtering out 'special transactions' like 'ADJUST_INTEREST' and 'ADJUST_PENALTY'
     def transactions(self, sql_session: Session) -> list[Transaction]:
         """
         Returns the transactions of the user in chronological order.
diff --git a/dibbler/queries/buy_product.py b/dibbler/queries/buy_product.py
deleted file mode 100644
index ec3bb1d..0000000
--- a/dibbler/queries/buy_product.py
+++ /dev/null
@@ -1,54 +0,0 @@
-import math
-from datetime import datetime
-
-from sqlalchemy.orm import Session
-
-from dibbler.models import (
-    Product,
-    Transaction,
-    User,
-)
-from dibbler.queries.current_interest import current_interest
-from dibbler.queries.current_penalty import current_penalty
-from dibbler.queries.user_balance import user_balance
-
-from .product_price import product_price
-
-
-def buy_product(
-    sql_session: Session,
-    user: User,
-    product: Product,
-    product_count: int,
-    time: datetime | None = None,
-    message: str | None = None,
-) -> Transaction:
-    """
-    Creates a BUY_PRODUCT transaction with the amount automatically calculated based on the product's current price.
-    """
-
-    # balance = user_balance(sql_session, user)
-
-    # price = product_price(sql_session, product)
-
-    # interest_rate = current_interest(sql_session)
-
-    # penalty_threshold, penalty_multiplier_percent = current_penalty(sql_session)
-
-    # price *= product_count
-
-    # price *= 1 + interest_rate / 100
-
-    # if balance < penalty_threshold:
-    #     price *= 1 + penalty_multiplier_percent / 100
-
-    # price = math.ceil(price)
-
-    return Transaction.buy_product(
-        time=time,
-        # amount=price,
-        user_id=user.id,
-        product_id=product.id,
-        product_count=product_count,
-        message=message,
-    )
diff --git a/dibbler/queries/product_price.py b/dibbler/queries/product_price.py
index e0c4d3d..46c2358 100644
--- a/dibbler/queries/product_price.py
+++ b/dibbler/queries/product_price.py
@@ -17,6 +17,7 @@ from dibbler.models import (
     TransactionType,
 )
 
+# TODO: include the transaction id in the log for easier debugging
 
 def _product_price_query(
     product_id: int,
@@ -121,6 +122,13 @@ def _product_price_query(
     return recursive_cte.union_all(recursive_elements)
 
 
+
+# TODO: create a function for the log that pretty prints the log entries
+#       for debugging purposes
+
+
+# TODO: wrap the log entries in a dataclass, the don't cost that much
+
 def product_price_log(
     sql_session: Session,
     product: Product,
diff --git a/dibbler/queries/product_stock.py b/dibbler/queries/product_stock.py
index cae94ec..8c591e5 100644
--- a/dibbler/queries/product_stock.py
+++ b/dibbler/queries/product_stock.py
@@ -1,3 +1,5 @@
+from datetime import datetime
+
 from sqlalchemy import case, func, select
 from sqlalchemy.orm import Session
 
@@ -11,13 +13,16 @@ from dibbler.models import (
 def product_stock(
     sql_session: Session,
     product: Product,
-    # use_cache: bool = True,
-    # until: datetime | None = None,
+    use_cache: bool = True,
+    until: datetime | None = None,
 ) -> int:
     """
     Returns the number of products in stock.
     """
 
+    if use_cache:
+        print("WARNING: Using cache for product stock query is not implemented yet.")
+
     result = sql_session.scalars(
         select(
             func.sum(
@@ -46,6 +51,7 @@ def product_stock(
                 ]
             ),
             Transaction.product_id == product.id,
+            Transaction.time <= until if until is not None else 1 == 1,
         )
     ).one_or_none()
 
diff --git a/dibbler/queries/search_product.py b/dibbler/queries/search_product.py
index 98161e3..771784d 100644
--- a/dibbler/queries/search_product.py
+++ b/dibbler/queries/search_product.py
@@ -4,6 +4,7 @@ from sqlalchemy.orm import Session
 from dibbler.models import Product
 
 
+# TODO: modernize queries to use SQLAlchemy 2.0 style
 def search_product(
     string: str,
     session: Session,
diff --git a/dibbler/queries/user_balance.py b/dibbler/queries/user_balance.py
index e35c068..5d2316f 100644
--- a/dibbler/queries/user_balance.py
+++ b/dibbler/queries/user_balance.py
@@ -26,6 +26,7 @@ from dibbler.models.Transaction import (
 )
 from dibbler.queries.product_price import _product_price_query
 
+# TODO: include the transaction id in the log for easier debugging
 
 def _user_balance_query(
     user: User,
@@ -197,6 +198,14 @@ def _user_balance_query(
     return recursive_cte.union_all(recursive_elements)
 
 
+# TODO: create a function for the log that pretty prints the log entries
+#       for debugging purposes
+
+# TODO: wrap the log entries in a dataclass, the don't cost that much
+
+# TODO: add a method on the dataclass, using the running penalization data
+#       to figure out if the current row was penalized or not.
+
 def user_balance_log(
     sql_session: Session,
     user: User,
@@ -233,7 +242,6 @@ def user_balance(
     sql_session: Session,
     user: User,
     use_cache: bool = True,
-    # Optional: calculate the balance until a certain transaction.
     until: Transaction | None = None,
 ) -> int:
     """