A company runs a batch analysis with transactional reporting every hour on its main transactional DB running on an RDS MySQL instance to populate its central Data Warehouse running on Redshift. During the execution of the batch, their transactional applications are very slow. When the batch completes, they need to update the top management dashboard with the new data. The dashboard is produced by another system running on-premises that is currently started when a manually-sent email notifies that an update is required. The on-premises system cannot be modified because it is managed by another team.

Answer options:

A.Replace RDS with Redshift for the batch analysis and SNS to notify the on-premises system to update the dashboard.
B.Replace RDS with Redshift for the batch analysis and SQS to send a message to the on-premises system to update the dashboard.
C.Create an RDS Read Replica for the batch analysis and SNS to notify the on-premises system to update the dashboard.
D.Create an RDS Read Replica for the batch analysis and SQS to send a message to the on-premises system to update the dashboard.

Answer - C
There are two architectural considerations here. (1) you need to improve read performance by reducing the load on the RDS MySQL instance, and (2) automate the process of notifying to the on-premise system.
When the scenario asks you to improve a DB instance`s read performance, always look for options such as ElastiCache or Read Replicas. And when the question asks you to automate the notification process, always think of using SNS. 
Options A and B are incorrect because replacing RDS with Redshift may need many changes on the applications and are not required in this scenario.
Option C is CORRECT because (a) it uses Read Replicas which improves the read performance, and (b) it uses SNS which automates the process of notifying the on-premise system to update the dashboard.
Option D is incorrect because SQS is not a service to be used for sending the notification.
For more information on Read Replica’s, please visit the below link-
https://aws.amazon.com/rds/details/read-replicas/