Another AutoScaling feature is predictive scaling, which uses machine learning to learn the scaling pattern of your application based on the minimum amount of historical data. The machine learning component then predicts the scaling after reviewing CW data from the previous 14 days to account for daily and weekly spikes as it learns the patterns on a longer time scale. Figure 4.6 illustrates predictive scaling.
FIGURE 4.6 Predictive scaling
Cram Quiz
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. Which of the following are not characteristics of a scalable/elastic application?
A. Synchronous request handling in the compute layer
B. Session persistence in an external database
C. Session persistence in the compute layer
D. Asynchronous request offloading to a message queue
2. Which of the following are required to enable the application to scale automatically with AWS AutoScaling? (Choose three.)
A. EC2 Launch Configuration
B. Scaling Policy
C. EC2 User Data
D. DynamoDB
E. CloudWatch Alarm
F. AutoScaling Group
3. True or False: After you assess that your application is fully scalable and elastic, you only need to maintain the application as is in the cloud.
4. True or False: AutoScaling supports only dynamic, scheduled, and predictive scaling.
1. Answer: C is correct. The compute layer should be made stateless. Any persistence in the compute layer hinders scalability and elasticity and potentially causes disruption in the application operation. If an instance in a cluster is lost, all the sessions on the instances are lost with it, meaning all the users connected to that particular instance have to log in and start working with the application from scratch.
2. Answer: A, B, and F are correct. To create an autoscaling configuration on EC2, you need an EC2 Launch Configuration that defines how to configure the EC2 instances that are launched; a scaling policy that determines the scaling thresholds; and an autoscaling group that determines the minimum, maximum, and desired numbers of instances.
3. Answer: False. The application should periodically be reassessed for scalability and elasticity because both the application requirements and the SLA might have changed.
4. Answer: False. Autoscaling also supports manual scaling by setting the desired number of instances in the autoscaling group.
This section covers the following official AWS Certified SysOps Administrator – Associate (SOA-C02) exam domains:
Domain 2: Reliability and Business Continuity
Domain 5: Networking and Content Delivery
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