Exam AWS Certified Database - Specialty topic 1 question 113 discussion

reduce cost - on-demand costlier predictable, gradual increase - auto scaling

C is correct based on documentation: When you create a DynamoDB table, auto scaling is the default capacity setting, but you can also enable auto scaling on any table that does not have it active. Behind the scenes, as illustrated in the following diagram, DynamoDB auto scaling uses a scaling policy in Application Auto Scaling. https://aws.amazon.com/blogs/database/amazon-dynamodb-auto-scaling-performance-and-cost-optimization-at-any-scale/

If C had been worded differently, like "Provisioned capacity with auto-scaling", I might have chosen C. But "AWS Application Auto-Scaling" does not make sense in the DynamoDB context. Therefore I choose "On-Demand" which is very flexible in terms of throughput.

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C for me too.. DynamoDB auto scaling uses a scaling policy in Application Auto Scaling. To configure auto scaling in DynamoDB, you set the minimum and maximum levels of read and write capacity in addition to the target utilization percentage. Auto scaling uses Amazon CloudWatch to monitor a table’s read and write capacity metrics. To do so, it creates CloudWatch alarms that track consumed capacity.

no traffic at night and orders of magnitude high traffic in off peak. I will go with D

C: As the pattern is predictable load with mangitude of spikes this could be handled by autoscaling. As per aws autoscaling is cost saving as compared to ondemand. If the pattern was unpredictable On-demand would be good

but it also says "traffic increase during peak hours is steady and predictable" and the firm also wants to reduce the throttling " so it is either C or D I think .. C is more likely as traffic pattern is predictable

It states that there is lot of throttling though out the day and the firm wants to minimize the expenditure and cost. Provisioned is costlier and during night hours the traffic is almost nill. So what ever small ( average of day ) capacity you are provisioning will be wasted at night. I believe on-demand in this case is better choice.

"... traffic increase during peak hours is steady and predictable ..."

- traffic increase during peak hours is steady and predictable=> provisioned - no uses in night. => on demand (but costly) so provision some + auto scale with a target 70% utilization set D will also work but costly

I go with C. "To understand how DynamoDB auto scaling works, suppose that you have a table named ProductCatalog. The table is bulk-loaded with data infrequently, so it doesn't incur very much write activity. However, it does experience a high degree of read activity, which varies over time. By monitoring the Amazon CloudWatch metrics for ProductCatalog, you determine that the table requires 1,200 read capacity units (to avoid DynamoDB throttling read requests when activity is at its peak). You also determine that ProductCatalog requires 150 read capacity units at a minimum, when read traffic is at its lowest point. Within the range of 150 to 1,200 read capacity units, you decide that a target utilization of 70 percent would be appropriate for the ProductCatalog table. Target utilization is the ratio of consumed capacity units to provisioned capacity units, expressed as a percentage. Application Auto Scaling uses its target tracking algorithm to ensure that the provisioned read capacity of ProductCatalog is adjusted as required so that utilization remains at or near 70 percent."

Very tricky. Feels like (D) Even of you enable Autoscaling - but you will still pay the same rate during off-peak hours. the provisioned capacity will never fall below the preconfigured one during night when theres no traffic. Plus the question WANTS to reduce expenditure - which means with OnDemand theres barely any charge during off peak hours compared to fully charged if u use provisioned capacity using thebaseline configured RCU/WCUs.

C Provisioned Mode If you choose provisioned mode, you specify the number of reads and writes per second that you require for your application. You can use auto scaling to adjust your table’s provisioned capacity automatically in response to traffic changes. This helps you govern your DynamoDB use to stay at or below a defined request rate in order to obtain cost predictability. Provisioned mode is a good option if any of the following are true: You have predictable application traffic. You run applications whose traffic is consistent or ramps gradually. You can forecast capacity requirements to control costs.

They know peak hours AWS Application Auto Scaling policy is good for it.

C. DynamoDB autoscaling saves costs comparing to on-demand (which costs a bit higher for the NoOps benefit.) https://aws.amazon.com/blogs/database/amazon-dynamodb-auto-scaling-performance-and-cost-optimization-at-any-scale/

"traffic increase during peak hours is steady and predictable" C is the answer.