Your company is hosting an application in AWS. The application is read-intensive and consists of a set of web servers and AWS RDS. It has been noticed that the response time of the application increases due to the load on the AWS RDS instance. Which of the following measures can be taken to scale the data tier? (SELECT TWO.)

Answer options:

A.Create Amazon DB Read Replicas. Configure the application layer to query the Read Replicas for query needs.
B.Use Auto Scaling to scale out the database tier.
C.Use SQS to cache the database queries.
D.Use ElastiCache in front of your Amazon RDS DB to cache common queries.

Correct Answers - A and D
AWS documentation mentions the following.
Amazon RDS Read Replicas provide enhanced performance and durability for database (DB) instances. This replication feature makes it easy to elastically scale out beyond a single DB Instance`s capacity constraints for read-heavy database workloads. You can create one or more replicas of a given source DB Instance and serve high-volume application read traffic from multiple copies of your data, thereby increasing aggregate read throughput. Read replicas can also be promoted when needed to become standalone DB instances.
For more information on AWS RDS Read Replica’s, please visit the URL below:
https://aws.amazon.com/rds/details/read-replicas/ 
Amazon ElastiCache is a web service that makes it easy to deploy, operate, and scale an in-memory data store or cache in the cloud. The service improves web applications` performance by allowing you to retrieve information from fast, managed, in-memory data stores instead of relying entirely on slower disk-based databases.
For more information on AWS ElastiCache, please visit the URL below.
https://aws.amazon.com/elasticache/