diff --git a/unimore_bda_6/config.py b/unimore_bda_6/config.py
index 5e5540d..eb93fc0 100644
--- a/unimore_bda_6/config.py
+++ b/unimore_bda_6/config.py
@@ -3,27 +3,34 @@ import cfig
 config = cfig.Configuration()
 
 
-@config.required()
-def MONGO_HOST(val: str) -> str:
+@config.optional()
+def MONGO_HOST(val: str | None) -> str:
     """
     The hostname of the MongoDB database to connect to.
     """
-    return val
+    return val or "127.0.0.1"
 
 
-@config.required()
-def MONGO_PORT(val: str) -> str:
+@config.optional()
+def MONGO_PORT(val: str | None) -> int:
     """
     The port of the MongoDB database to connect to.
     """
-    return val
+    if not val:
+        return 27017
+    try:
+        return int(val)
+    except ValueError:
+        raise cfig.InvalidValueError("Not an int.")
 
 
-@config.required()
-def TRAINING_SET_SIZE(val: str) -> int:
+@config.optional()
+def TRAINING_SET_SIZE(val: str | None) -> int:
     """
     The number of reviews from each category to fetch for the training set.
     """
+    if not val:
+        return 1000
     try:
         return int(val)
     except ValueError: