A company is running web server reserved EC2 Instances with EBS-backed root volumes. These instances have a consistent CPU load of 80%. Traffic is being distributed to these instances by an Elastic Load Balancer. They also have Multi-AZ RDS MySQL databases in both development and production environments. What recommendation would you make to reduce cost without affecting the availability of mission-critical systems? Choose the correct answer from the options given below.

Answer options:

A.Consider using On-demand instances instead of Reserved EC2 instances.
B.Consider not using the Multi-AZ RDS deployment for the database in the development environment.
C.Consider using Spot instances instead of Reserved EC2 instances.
D.Consider removing the Elastic Load Balancer.

Correct Answer – B
Multi-AZ databases are more suitable for production environments than for development environments. So you can reduce costs by not using these for development environments.
Amazon RDS Multi-AZ deployments provide enhanced availability and durability for Database (DB) Instances, making them a natural fit for production database workloads. When you provision a Multi-AZ DB Instance, Amazon RDS automatically creates a primary DB Instance and synchronously replicates the data to a standby instance in a different Availability Zone (AZ). Each AZ runs on its own physically distinct, independent infrastructure and is engineered to be highly reliable. In case of an infrastructure failure, Amazon RDS performs an automatic failover to the standby (or to a read replica in the case of Amazon Aurora). Thus you can resume database operations as soon as the failover is complete. Since the endpoint for your DB Instance remains the same after a failover, your application can resume database operation without the need for manual administrative intervention.
For more information on Multi-AZ RDS, please refer to the link below:
https://aws.amazon.com/rds/details/multi-az/
Note:
Mission Critical system refers to production Instances and Databases. However, if you notice, they have Multi-AZ RDS in the Development environment, which is unnecessary. Because management is always concerned about production, the environment should be perfect. 
To reduce the cost, we can disable the Multi-AZ RDS for the Development environment and keep it only for the Production environment.