Your company has an application hosted in AWS. This application consists of a web tier and database tier. The web tier is hosted on EC2 Instances. The database is hosted in the AWS RDS service, and data keeps changing every few hours. Recently performance issues have been encountered in the application, which is due to the high number of read requests. Which of the following can be used to help resolve the issue?

Answer options:

A.Enable Multi-AZ for the database
B.Use Read Replica
C.Use Amazon DynamoDB Accelerator (DAX)
D.Place an Elastic Cache service in front of the database service

Answer –B
In terms of load, they have the same goal, but they differ in some areas:
Up-to-dateness of data:
A read replica will continuously sync from the master. So your results will probably lag 0 - 3s (depending on the load) behind the master.
A cache takes the query result at a specific point in time and stores it for a certain amount of time.
Performance:
A cache can only return results for queries it has already seen. So if you run the same queries over and over again, it`s a good match.
If you have many different, frequently changing, or dynamic queries, a read replica will be a better match.
ElastiCache should be much faster since it`s returning values directly from RAM. However, this also limits the number of results you can store.
Option B is correct since the question specifies data keeps frequently changing, as it keeps data up-to-date and read performance is also improved.
ElastiCache can be used to reduce the latency of requests. Still, it is a caching service. According to the question, data keeps changing every few hours, so Elasticache is not recommended choice.
Option A is incorrect since this is used for high availability for the databases.
Option C is incorrect since Amazon DynamoDB Accelerator (DAX) is a Fully managed, in-memory cache for DynamoDB only.
For more information on Read Replica and Elasticache, please refer to the below URLs-
https://aws.amazon.com/rds/features/read-replicas/
https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/elasticache-use-cases.htm