Correct answer - "Setup ElastiCache in front of RDS" : Amazon ElastiCache is an ideal front-end
for data stores such as Amazon RDS, providing a high-performance middle tier for applications
with extremely high request rates and/or low latency requirements.
"Setup RDS Read Replicas" - A replica continually syncs from the master database but its not
suitable for an application where clients retrieve the same data over and over, this is where a
cache system like ElastiCache helps
"Use Redshift" - It is optimized for datasets ranging from a few hundred gigabytes to a petabyte
or more
"Switch your application code to AWS Lambda" - You will have to change code if you go with AWS
Lambda however changing the code does not address the heavy load on the database and putting a
front-end data store such as ElastiCache it is more of a fit solution