From ffa9565ab8aa540647b83319b0521cf768a512d4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9rgio=20Rafael=20Siqueira?=
 <osergiosiqueira@gmail.com>
Date: Wed, 3 Dec 2025 10:53:23 -0300
Subject: [PATCH] add check mx record

---
 .../app/events/batch/chunks_into_users.py     |  1 -
 users-events/app/events/check_mx_record.py    | 45 +++++++++++++++++++
 users-events/template.yaml                    | 24 ++++++++++
 .../tests/events/test_check_mx_record.py      | 20 +++++++++
 4 files changed, 89 insertions(+), 1 deletion(-)
 create mode 100644 users-events/app/events/check_mx_record.py
 create mode 100644 users-events/tests/events/test_check_mx_record.py

diff --git a/users-events/app/events/batch/chunks_into_users.py b/users-events/app/events/batch/chunks_into_users.py
index c3fb1ff..52c0eb9 100644
--- a/users-events/app/events/batch/chunks_into_users.py
+++ b/users-events/app/events/batch/chunks_into_users.py
@@ -152,7 +152,6 @@ def _create_user(rawuser: dict, context: dict) -> None:
                 'sk': f'emails#{user.email}',
                 'email_verified': False,
                 'email_primary': True,
-                'mx_record_exists': False,
                 'created_at': now_,
             }
         )
diff --git a/users-events/app/events/check_mx_record.py b/users-events/app/events/check_mx_record.py
new file mode 100644
index 0000000..682acd7
--- /dev/null
+++ b/users-events/app/events/check_mx_record.py
@@ -0,0 +1,45 @@
+from aws_lambda_powertools import Logger
+from aws_lambda_powertools.utilities.data_classes import (
+    EventBridgeEvent,
+    event_source,
+)
+from aws_lambda_powertools.utilities.typing import LambdaContext
+from email_validator import EmailUndeliverableError, validate_email
+from layercake.dateutils import now
+from layercake.dynamodb import DynamoDBPersistenceLayer, KeyPair
+
+from boto3clients import dynamodb_client
+from config import USER_TABLE
+
+logger = Logger(__name__)
+dyn = DynamoDBPersistenceLayer(USER_TABLE, dynamodb_client)
+
+
+@event_source(data_class=EventBridgeEvent)
+@logger.inject_lambda_context
+def lambda_handler(event: EventBridgeEvent, context: LambdaContext) -> bool:
+    new_image = event.detail['new_image']
+    # Post-migration (users): rename `emails` to `EMAIL`
+    email = new_image['sk'].removeprefix('emails#')
+
+    return dyn.update_item(
+        key=KeyPair(
+            pk=new_image['id'],
+            sk=new_image['sk'],
+        ),
+        update_expr='SET mx_record_exists = :bool, \
+                         updated_at = :now',
+        expr_attr_values={
+            ':bool': _mx_record_exists(email),
+            ':now': now(),
+        },
+    )
+
+
+def _mx_record_exists(email: str) -> bool:
+    try:
+        validate_email(email, check_deliverability=True)
+    except EmailUndeliverableError:
+        return False
+    else:
+        return True
diff --git a/users-events/template.yaml b/users-events/template.yaml
index d68281f..19beb0b 100644
--- a/users-events/template.yaml
+++ b/users-events/template.yaml
@@ -221,3 +221,27 @@ Resources:
                     - prefix: EMAIL_VERIFICATION#
                   welcome:
                     - exists: false
+
+  EventCheckMxRecordFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: events.check_mx_record.lambda_handler
+      LoggingConfig:
+        LogGroup: !Ref EventLog
+      Timeout: 12
+      Policies:
+        - DynamoDBCrudPolicy:
+            TableName: !Ref UserTable
+      Events:
+        DynamoDBEvent:
+          Type: EventBridgeRule
+          Properties:
+            Pattern:
+              resources: [!Ref UserTable]
+              detail-type: [INSERT]
+              detail:
+                new_image:
+                  sk:
+                    - prefix: emails#
+                  mx_record_exists:
+                    - exists: false
diff --git a/users-events/tests/events/test_check_mx_record.py b/users-events/tests/events/test_check_mx_record.py
new file mode 100644
index 0000000..12ea165
--- /dev/null
+++ b/users-events/tests/events/test_check_mx_record.py
@@ -0,0 +1,20 @@
+from aws_lambda_powertools.utilities.typing.lambda_context import LambdaContext
+from layercake.dynamodb import DynamoDBPersistenceLayer
+
+import events.check_mx_record as app
+
+
+def test_check_mx_record(
+    lambda_context: LambdaContext,
+    dynamodb_persistence_layer: DynamoDBPersistenceLayer,
+):
+    event = {
+        'detail': {
+            'new_image': {
+                'id': '123',
+                'sk': 'emails#sergio@somosbeta.com.br',
+            },
+        },
+    }
+
+    assert app.lambda_handler(event, lambda_context)  # type: ignore