diff --git a/src/data_processing/transformations.py b/src/data_processing/transformations.py
index 2a643e8..0cae6b5 100644
--- a/src/data_processing/transformations.py
+++ b/src/data_processing/transformations.py
@@ -11,27 +11,30 @@ def pivot_table(
 
         def agg_func(values):
             return sum(values) / len(values)
+
     elif aggfunc == "sum":
 
         def agg_func(values):
             return sum(values)
+
     elif aggfunc == "count":
 
         def agg_func(values):
             return len(values)
+
     else:
         raise ValueError(f"Unsupported aggregation function: {aggfunc}")
     grouped_data = {}
-    for i in range(len(df)):
-        row = df.iloc[i]
-        index_val = row[index]
-        column_val = row[columns]
-        value = row[values]
-        if index_val not in grouped_data:
-            grouped_data[index_val] = {}
-        if column_val not in grouped_data[index_val]:
-            grouped_data[index_val][column_val] = []
-        grouped_data[index_val][column_val].append(value)
+
+    # Extract data as numpy arrays for fast iteration, avoiding .iloc row lookup
+    index_data = df[index].values
+    column_data = df[columns].values
+    value_data = df[values].values
+
+    for index_val, column_val, value in zip(index_data, column_data, value_data):
+        inner = grouped_data.setdefault(index_val, {})
+        inner.setdefault(column_val, []).append(value)
+
     for index_val in grouped_data:
         result[index_val] = {}
         for column_val in grouped_data[index_val]: