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Difficulty: MediumResilient Database Configurations and High Availability

A logistics tracking company operates a fleet management system on AWS with a write-intensive workload. The backend database is an Amazon RDS for PostgreSQL DB instance. The architecture team wants to design a resilient database setup that survives an Availability Zone outage with a Recovery Time Objective (RTO) of under 2 minutes and a Recovery Point Objective (RPO) of 0 (no data loss). In addition, they must offload heavy read-only reporting queries from the primary database to ensure write operations are unaffected. Which database configuration should a solutions architect recommend?

  1. A
    Deploy a Single-AZ Amazon RDS for PostgreSQL DB instance, and create a Read Replica in a different Availability Zone. Configure the application to promote the Read Replica to primary in the event of an outage.
  2. B
    Deploy an Amazon RDS for PostgreSQL Multi-AZ DB instance deployment. Configure Amazon Route 53 latency routing to distribute the reporting read queries between the primary instance and the standby instance in the secondary Availability Zone.
  3. Deploy an Amazon RDS for PostgreSQL Multi-AZ DB cluster with one primary writer instance and two readable standby DB instances.Answer
  4. D
    Deploy a Single-AZ Amazon RDS for PostgreSQL DB instance. Configure AWS Database Migration Service (AWS DMS) to continuously replicate data to a warm standby instance in another Availability Zone, and use this instance for reporting queries.

Answer

Deploy an Amazon RDS for PostgreSQL Multi-AZ DB cluster with one primary writer instance and two readable standby DB instances.
Deploying an Amazon RDS Multi-AZ DB cluster meets all requirements. It uses semi-synchronous replication to write data to two standby DB instances in different Availability Zones, guaranteeing a Recovery Point Objective (RPO) of 0. It also provides automatic failover in the event of an outage in less than 2 minutes (typically 35 to 75 seconds), meeting the Recovery Time Objective (RTO). Finally, because both standby instances are readable, they can serve read traffic to handle read scaling, eliminating the need to provision separate read replicas.

Step-by-Step Solution

1
Analyze the recovery objectives (RTO < 2 minutes, RPO = 0) and scaling requirements (must scale read traffic).
Identify that the database configuration must support synchronous or semi-synchronous replication for RPO = 0, fast automated failover for RTO < 2 minutes, and active readable secondary nodes to scale reads.
This establishes the constraints that the chosen database solution must satisfy.
2
Evaluate Amazon RDS deployment options against these constraints.
A standard Multi-AZ DB instance deployment supports RPO = 0 and automatic failover, but its standby is passive and cannot serve reads. An RDS Multi-AZ DB cluster uses semi-synchronous replication (RPO = 0), performs automated failover in 35-75 seconds (RTO < 2 minutes), and contains two readable standby instances.
Comparing available RDS architectures helps select the one that meets both high availability and read scaling out-of-the-box.
3
Select the configuration that minimizes administrative overhead.
The Amazon RDS Multi-AZ DB cluster provides a single reader endpoint to load balance queries across the readable standbys without requiring manual setup of separate read replicas or promotion scripts.
Choosing the cluster option meets all performance and resiliency criteria with the least configuration effort.

Key Concept

Amazon RDS Multi-AZ DB clusters provide high availability, automatic failover, and read scaling by utilizing two readable standby DB instances across different Availability Zones.
Estimated Time:2m 0s
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Resilient Database Configurations and High Availability

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