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What should the company do to eliminate this application performance issue?

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Lloyd
(@salterslloyd)
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A company is using an Amazon Aurora PostgreSQL DB cluster with an xlarge primary instance master and two large Aurora Replicas for high availability and read-only workload scaling. A failover event occurs and application performance is poor for several minutes. During this time, application servers in all Availability Zones are healthy and responding normally.

What should the company do to eliminate this application performance issue?

  • A . Configure both of the Aurora Replicas to the same instance class as the primary DB instance. Enable cache coherence on the DB cluster, set the primary DB instance failover priority to tier-0, and assign a failover priority of tier-1 to the replicas.
  • B . Deploy an AWS Lambda function that calls the DescribeDBInstances action to establish which instance has failed, and then use the PromoteReadReplica operation to promote one Aurora Replica to be the primary DB instance. Configure an Amazon RDS event subscription to send a notification to an Amazon SNS topic to which the Lambda function is subscribed.
  • C . Configure one Aurora Replica to have the same instance class as the primary DB instance. Implement Aurora PostgreSQL DB cluster cache management. Set the failover priority to tier-0 for the primary DB instance and one replica with the same instance class. Set the failover priority to tier-1 for the other replicas.
  • D . Configure both Aurora Replicas to have the same instance class as the primary DB instance. Implement Aurora PostgreSQL DB cluster cache management. Set the failover priority to tier-0 for the primary DB instance and to tier-1 for the replicas.

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Suggested Answer: C

Explanation:

https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraPostgreSQL.cluster-cache-mgmt.html

https://aws.amazon.com/blogs/database/introduction-to-aurora-postgresql-cluster-cache-management/

"You can customize the order in which your Aurora Replicas are promoted to the primary instance after a failure by assigning each replica a priority. Priorities range from 0 for the first priority to 15 for the last priority. If the primary instance fails, Amazon RDS promotes the Aurora Replica with the better priority to the new primary instance. You can modify the priority of an Aurora Replica at any time. Modifying the priority doesn't trigger a failover. More than one Aurora Replica can share the same priority, resulting in promotion tiers. If two or more Aurora Replicas share the same priority, then Amazon RDS promotes the replica that is largest in size. If two or more Aurora Replicas share the same priority and size, then Amazon RDS promotes an arbitrary replica in the same promotion tier. "

Amazon Aurora with PostgreSQL compatibility now supports cluster cache management, providing a faster path to full performance if there's a failover. With cluster cache management, you designate a specific reader DB instance in your Aurora PostgreSQL cluster as the failover target. Cluster cache management keeps the data in the designated reader's cache synchronized with the data in the read-write instance's cache. If a failover occurs, the designated reader is promoted to be the new read-write instance, and workloads benefit immediately from the data in its cache.

   
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