Answer these questions. The answers follow the last question. If you cannot answer these questions correctly, consider reading this section again until you can.
1. You have been instructed to eliminate any inefficiencies in the following deployment:
Web tier: EC2 autoscaling group scaling on CPU usage, 30% floor, 70% ceiling, minimum 1, maximum 10.
App tier: EC2 autoscaling group scaling on CPU usage, 20% floor, 80% ceiling, minimum 1, maximum 6.
Cache tier: 1 ElastiCache Memcached cluster with 2 partitions
Database tier: Multi-AZ MySQL RDS with 3 read replicas
Which of the following would allow you to cost optimize the cluster? (Choose all that apply.)
A. Evaluate whether all RDS read replicas are required.
B. Evaluate the maximum on the App and Web EC2 autoscaling groups.
C. Evaluate the partition configuration of the ElastiCache cluster.
D. Evaluate the network performance if the app tier matches the network performance of the database tier.
2. You have been asked to propose a solution to scale the read portion of an application database back end in the most cost-effective manner possible. Your application runs Linux LAMP stack with a 30 GB MySQL RDS Multi-AZ back end. The read-heavy operations are very predictable and occur during a particularly heavy four-hour operation each week and require the whole dataset. Which option would you recommend?
A. Replace the RDS MySQL with Aurora MySQL and let Aurora add read replicas automatically as needed.
B. Point the read-heavy operation at the RDS Multi-AZ replica in the other availability zone.
C. Deploy a read replica in RDS. Point the application at the RDS read replica. Terminate the read replica after the read-heavy operation is complete. Repeat the process with a script next week.
D. Deploy a read replica in RDS. Point the application at the RDS read replica. Create a script that powers off the read replica after the read-heavy operation is complete and powers it on before the next operation with enough time to synchronize the changes.
1. Answer: A and C are correct. You should always evaluate whether the read replicas and caching clusters you deployed are required and properly scaled.
2. Answer: C is correct. Although A and D are possible solutions, deploying a read replica on a weekly basis would be the most cost-effective way to achieve this goal because the operation is sparse in nature and lasts for only four hours. Deploying a read replica is performed from a snapshot and can be just as fast or even faster than replicating a week’s worth of data to the powered-off replica. Although the charges of powered-off instances are reduced, they are not zero. Remember also that you can stop a DB instance for up to seven days. If you don’t manually start your DB instance after seven days, your DB instance is automatically started so that it doesn’t fall behind any required maintenance updates. B is impossible because a Multi-AZ replica is not accessible for any SQL operations.
If you want more practice on this chapter’s exam objectives before you move on, remember that you can access all of the Cram Quiz questions on the Pearson Test Prep software online. You can also create a custom exam by objective with the Online Practice Test. Note any objective you struggle with and go to that objective’s material in this chapter.
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