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DBS-C01 · Question #209

A company has deployed an application that uses an Amazon RDS for MySQL DB cluster. The DB cluster uses three read replicas. The primary DB instance is an 8XL-sized instance, and the read replicas…

The correct answer is B. Migrate the primary DB instance to an Amazon Aurora MySQL DB cluster and add three Aurora E. Increase the instance size of the read replicas to the same size and class as the primary DB. Read replicas should be of the same size and class as primary DB. https://aws.amazon.com/premiumsupport/knowledge-center/rds-mysql-high-replica-lag/ Aurora seems to be better in handling the lags. Aurora-Read-replica

Submitted by asante_acc· Mar 6, 2026Workload-Specific Database Design

Question

A company has deployed an application that uses an Amazon RDS for MySQL DB cluster. The DB cluster uses three read replicas. The primary DB instance is an 8XL-sized instance, and the read replicas are each XL-sized instances. Users report that database queries are returning stale data. The replication lag indicates that the replicas are 5 minutes behind the primary DB instance. Status queries on the replicas show that the SQL_THREAD is 10 binlogs behind the IO_THREAD and that the IO_THREAD is 1 binlog behind the primary. Which changes will reduce the lag? (Choose two.)

Options

  • ADeploy two additional read replicas matching the existing replica DB instance size.
  • BMigrate the primary DB instance to an Amazon Aurora MySQL DB cluster and add three Aurora
  • CMove the read replicas to the same Availability Zone as the primary DB instance.
  • DIncrease the instance size of the primary DB instance within the same instance class.
  • EIncrease the instance size of the read replicas to the same size and class as the primary DB

How the community answered

(35 responses)
  • A
    6% (2)
  • B
    60% (21)
  • C
    20% (7)
  • D
    14% (5)

Explanation

Read replicas should be of the same size and class as primary DB. https://aws.amazon.com/premiumsupport/knowledge-center/rds-mysql-high-replica-lag/ Aurora seems to be better in handling the lags. Aurora-Read-replica

Topics

#RDS MySQL#Replication lag#Aurora MySQL#Read replica scaling

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