diff --git a/update_cars.py b/update_cars.py
index cb979f8..53ce8aa 100644
--- a/update_cars.py
+++ b/update_cars.py
@@ -1,48 +1,40 @@
 import asyncio
-from typing import List
+from typing import List, Dict, Any
+
+from pymongo import ASCENDING, IndexModel, collection
+from pymongo.collection import Collection
 
 import updater
 from db import MongoDBConnection
 
 
-async def main():
-    collection_name: str = "cars"
-    zip_file_name: str = "Monthly New Registration of Cars by Make.zip"
-    zip_url: str = (
-        f"https://datamall.lta.gov.sg/content/dam/datamall/datasets/Facts_Figures/Vehicle Registration/{zip_file_name}"
-    )
-    key_fields: List[str] = ["month"]
+async def create_indexes(collection: Collection) -> None:
+    indexes = [
+        IndexModel([("month", ASCENDING), ("make", ASCENDING)]),
+        IndexModel([("month", ASCENDING)]),
+        IndexModel([("make", ASCENDING)]),
+        IndexModel([("fuel_type", ASCENDING)]),
+        IndexModel([("make", ASCENDING), ("fuel_type", ASCENDING)]),
+        IndexModel([("number", ASCENDING)]),
+    ]
+    collection.create_indexes(indexes)
 
-    db = MongoDBConnection().database
-    collection = db[collection_name]
 
-    # Create indexes
-    collection.create_index({"month": 1, "make": 1})
-    collection.create_index({"month": 1})
-    collection.create_index({"make": 1})
-    collection.create_index({"fuel_type": 1})
-    collection.create_index({"make": 1, "fuel_type": 1})
-    collection.create_index({"number": 1})
-
-    message = await updater.main(collection_name, zip_file_name, zip_url, key_fields)
-
-    if message["inserted_count"] > 0:
-        print("Running aggregation...")
-
-        replace_empty_string_with_zero = [
+async def run_aggregations(collection: Collection) -> None:
+    aggregations = [
+        [
             {"$match": {"number": ""}},
             {"$set": {"number": 0}},
             {
                 "$merge": {
-                    "into": collection_name,
+                    "into": collection.name,
                     "on": "_id",
                     "whenMatched": "replace",
                     "whenNotMatched": "discard",
                 }
             },
-        ]
-
-        format_values = [
+        ],
+        [
             {
                 "$addFields": {
                     "make": {
@@ -50,7 +42,7 @@ async def main():
                             "input": "$make",
                             "find": ".",
                             "replacement": "",
-                        },
+                        }
                     },
                     "vehicle_type": {
                         "$replaceAll": {
@@ -63,30 +55,48 @@ async def main():
             },
             {
                 "$merge": {
-                    "into": collection_name,
+                    "into": collection.name,
                     "on": "_id",
                     "whenMatched": "merge",
                     "whenNotMatched": "discard",
                 }
             },
-        ]
-
-        uppercase_make = [
+        ],
+        [
             {"$addFields": {"make": {"$toUpper": "$make"}}},
             {
                 "$merge": {
-                    "into": collection_name,
+                    "into": collection.name,
                     "on": "_id",
                     "whenMatched": "merge",
                     "whenNotMatched": "discard",
                 }
             },
-        ]
+        ],
+    ]
+
+    for aggregation in aggregations:
+        collection.aggregate(aggregation)
+
 
-        collection.aggregate(replace_empty_string_with_zero)
-        collection.aggregate(format_values)
-        collection.aggregate(uppercase_make)
+async def main() -> Dict[str, Any]:
+    collection_name: str = "cars"
+    zip_file_name: str = "Monthly New Registration of Cars by Make.zip"
+    zip_url: str = (
+        f"https://datamall.lta.gov.sg/content/dam/datamall/datasets/Facts_Figures/Vehicle Registration/{zip_file_name}"
+    )
+    key_fields: List[str] = ["month"]
 
+    db = MongoDBConnection().database
+    collection = db[collection_name]
+
+    await create_indexes(collection)
+
+    message = await updater.main(collection_name, zip_file_name, zip_url, key_fields)
+
+    if message["inserted_count"] > 0:
+        print("Running aggregation...")
+        await run_aggregations(collection)
         print("Aggregation complete.")
 
     db.client.close()
diff --git a/updater.py b/updater.py
index d1b01c4..5e4434d 100644
--- a/updater.py
+++ b/updater.py
@@ -3,9 +3,10 @@
 import os
 import tempfile
 import time
-from typing import List, Dict, Any
+from typing import List, Dict, Any, Tuple
 
 from dotenv import load_dotenv
+from pymongo.results import InsertManyResult
 
 from db import MongoDBConnection
 from download_file import download_file
@@ -16,17 +17,13 @@
 
 
 def read_csv_data(file_path: str) -> List[Dict[str, Any]]:
-    csv_data = []
     with open(file_path, "r", encoding="utf-8") as csv_file:
-        csv_reader = csv.DictReader(csv_file)
-        for row in csv_reader:
-            csv_data.append(row)
-    return csv_data
+        return list(csv.DictReader(csv_file))
 
 
 async def updater(
     collection_name: str, zip_file_name: str, zip_url: str, key_fields: List[str]
-) -> tuple[Any, str] | tuple[None, str]:
+) -> Tuple[InsertManyResult | None, str]:
     db = MongoDBConnection().database
     collection = db[collection_name]
 
@@ -55,7 +52,6 @@ async def updater(
                 start = time.time()
                 result = collection.insert_many(new_data_to_insert)
                 end = time.time()
-                db.client.close()
                 message = f"{len(result.inserted_ids)} document(s) inserted in {round((end - start) * 1000)}ms"
                 return result, message
             else:
@@ -63,8 +59,9 @@ async def updater(
                 return None, message
 
     except Exception as error:
-        print(f"An error has occurred: {error}")
-        raise
+        raise Exception(f"An error has occurred: {error}")
+    finally:
+        db.client.close()
 
 
 async def main(