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Difficulty: MediumCost-Optimized Database Design and Capacity Planning

A company runs a read-heavy reporting application on AWS. The application uses an Amazon RDS for PostgreSQL DB instance to store analytical data. The database requires high read throughput during weekly reporting windows, but does not have strict high availability (HA) or automatic failover requirements for write operations. The database is currently configured as a Multi-AZ DB instance. A solutions architect needs to optimize the database configuration to reduce monthly costs while maintaining read performance.

Which TWO actions should the solutions architect take to achieve this goal? (Select TWO.)

  1. Modify the RDS DB instance from a Multi-AZ deployment to a Single-AZ deployment.Answer
  2. Create one or more RDS Read Replicas in different Availability Zones to handle the read-heavy reporting queries.Answer
  3. C
    Keep the Multi-AZ deployment and purchase a 33-year Compute Savings Plan to discount the database instance costs.
  4. D
    Migrate the PostgreSQL database to an Amazon DynamoDB table configured in Provisioned Capacity mode.
  5. E
    Convert the database to a Single-AZ deployment and configure an RDS Read Replica as the primary, automatic disaster recovery failover target.

Answer

Modify the RDS DB instance from a Multi-AZ deployment to a Single-AZ deployment, and create one or more RDS Read Replicas in different Availability Zones to handle the read-heavy reporting queries.
The correct solution involves modifying the Amazon RDS DB instance to a Single-AZ deployment because the workload does not require high availability for write operations. To cost-effectively scale read throughput during weekly reporting windows, the solutions architect should deploy one or more RDS Read Replicas, which offload read queries from the primary instance.

Step-by-Step Solution

1
Analyze database write availability requirements
Identify that the application does not have strict high availability or automatic failover requirements for write operations.
This allows the removal of the synchronous Multi-AZ standby instance, which halves the base database instance costs.
2
Identify database read scaling requirements
Determine that read capacity needs to scale during weekly reporting windows.
Deploying cost-effective Read Replicas meets the read scaling requirements horizontally without paying for a full Multi-AZ write standby.
3
Evaluate and eliminate incorrect cost optimization options
Eliminate Compute Savings Plans (which do not apply to RDS) and DynamoDB (which requires schema redesign and has high costs for spiky workloads in Provisioned mode).
This confirms the selected options are the most cost-effective and operationally feasible solutions.

Key Concept

RDS Multi-AZ vs. Single-AZ with Read Replicas
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Topics

Cost-Optimized Database Design and Capacity Planning