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Difficulty: MediumResilient Database Configurations and High Availability

A financial services company runs a critical transactional application backed by an Amazon RDS PostgreSQL DB instance. Currently, the database is deployed in a single Availability Zone (AZ). Due to compliance regulations, the database layer must be redesigned to ensure high availability. The solution must achieve a Recovery Point Objective (RPO) of zero (no data loss) and a Recovery Time Objective (RTO) of under two minutes in the event of an AZ failure. Which database configuration should a solutions architect recommend to meet these requirements?

  1. Modify the existing Amazon RDS DB instance to be a Multi-AZ deployment.Answer
  2. B
    Create an Amazon RDS Read Replica in a different Availability Zone, and configure a custom monitoring script to promote the read replica to primary if the primary instance fails.
  3. C
    Deploy a warm standby Amazon RDS PostgreSQL DB instance in a different AWS Region, and use AWS Database Migration Service (AWS DMS) to continuously replicate data.
  4. D
    Deploy an Amazon RDS Read Replica in a second Availability Zone, and configure Amazon Route 53 latency-based routing to automatically fail over database connection endpoints.

Answer

Modify the existing Amazon RDS DB instance to be a Multi-AZ deployment.
Modifying the existing DB instance to a Multi-AZ deployment matches all criteria. It synchronously replicates database changes to a standby instance in a different Availability Zone, ensuring zero data loss (RPO = 0). If the primary instance fails, Amazon RDS automatically performs a failover by updating the database DNS CNAME record to point to the standby instance, which typically takes between one and two minutes (RTO < 2 minutes).

Step-by-Step Solution

1
Analyze the requirements for high availability, specifically the RPO (Recovery Point Objective) of zero and RTO (Recovery Time Objective) of under two minutes.
Identified that the replication must be synchronous to ensure no data loss (RPO = 0), and the failover mechanism must be automatic and fast (RTO < 2 minutes).
This sets the baseline criteria to evaluate the available database configurations.
2
Evaluate the replication type of Amazon RDS options.
Multi-AZ deployments use synchronous replication to a standby instance in a different AZ, whereas Read Replicas use asynchronous replication.
Only synchronous replication can guarantee an RPO of zero (no data loss) during an unexpected primary node failure.
3
Evaluate the failover mechanisms of the proposed solutions.
Multi-AZ deployments perform automatic DNS failover to the standby replica, typically completing within 60-120 seconds. Promoting a read replica or cross-region warm standby is a manual process or requires complex custom scripting, which increases RTO.
Ensures that the configuration meets the RTO requirement of under two minutes.

Key Concept

Amazon RDS Multi-AZ deployments provide high availability, data redundancy, and automatic failover by utilizing synchronous replication to a standby instance in a different Availability Zone.
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Topics

Resilient Database Configurations and High Availability

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