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Difficulty: HardResilient Database Configurations and High Availability

An e-commerce company is migrating its primary transactional database to Amazon RDS for MySQL. The database design must meet the following operational requirements:

* Within the primary AWS Region, the database must support automatic failover with a Recovery Time Objective (RTO) of less than 4040 seconds.
* The architecture must allow read workloads to scale horizontally across multiple Availability Zones in the primary Region without querying the primary writer instance.
* For disaster recovery, the database must support cross-Region replication to a secondary Region with a Recovery Point Objective (RPO) of less than 1515 minutes.

Which database configuration meets these requirements with the least operational complexity?

  1. Deploy an Amazon RDS Multi-AZ DB cluster containing one primary writer and two readable standby instances across three Availability Zones. Configure an asynchronous cross-Region read replica in the secondary Region.Answer
  2. B
    Deploy an Amazon RDS Multi-AZ DB instance containing one primary writer and one non-readable standby instance. Create two read replicas in the primary Region for read scaling, and create a cross-Region read replica. Configure Amazon Route 53 latency-based routing to automatically redirect write traffic to the read replicas if the primary writer fails.
  3. C
    Deploy an Amazon RDS Single-AZ DB instance with two read replicas in the primary Region and one cross-Region read replica in the secondary Region. Configure Route 53 failover routing with active-passive health checks to automatically promote a primary Region read replica to master if the Single-AZ instance fails.
  4. D
    Deploy an Amazon RDS Multi-AZ DB instance in the primary Region. Configure AWS Backup to perform cross-Region replication of the database snapshots to the secondary Region every 1212 hours. Restore the database from the copied snapshot in the secondary Region during a disaster recovery scenario.

Answer

Deploy an Amazon RDS Multi-AZ DB cluster containing one primary writer and two readable standby instances across three Availability Zones. Configure an asynchronous cross-Region read replica in the secondary Region.
The configuration utilizing an Amazon RDS Multi-AZ DB cluster satisfies all operational requirements. It provides a primary writer and two readable standby instances across three Availability Zones. Failover in a Multi-AZ DB cluster is typically completed in under 3535 seconds (meeting the 4040-second RTO limit). Additionally, because both standby instances are readable, the application can scale read workloads without querying the primary writer. A cross-Region read replica provides asynchronous, near-real-time replication, meeting the RPO of less than 1515 minutes.

Step-by-Step Solution

1
Analyze the local high availability and RTO requirement.
An RTO of less than 4040 seconds rules out standard RDS Multi-AZ DB instances (which take 6060 to 120120 seconds to failover) and Single-AZ instances. An RDS Multi-AZ DB cluster uses semi-synchronous replication with a failover time of under 3535 seconds, meeting the target.
Determining the correct local deployment configuration is critical to meeting the low RTO threshold.
2
Evaluate the read-scaling requirement in the primary Region.
Standard RDS Multi-AZ DB instances have a passive, non-readable standby. An RDS Multi-AZ DB cluster features two readable standby instances that can serve read traffic directly, reducing operational complexity compared to provisioning separate read replicas.
Identifying the scaling capabilities of readable standby instances versus passive standby instances ensures read requirements are met efficiently.
3
Evaluate the cross-Region disaster recovery and RPO requirement.
An RPO of less than 1515 minutes requires continuous or near-continuous replication. An asynchronous cross-Region read replica continuously replicates data from the primary cluster, providing a low RPO (usually seconds). Replicating snapshots every 1212 hours fails this RPO.
Verifying the replication mechanism ensures the RPO constraint is satisfied.

Key Concept

Selecting between Amazon RDS Multi-AZ DB instances, Multi-AZ DB clusters, and cross-Region read replicas to satisfy strict RTO, RPO, and read scaling requirements.
Estimated Time:2m 30s
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Topics

Resilient Database Configurations and High Availability

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