Exam AWS Certified Solutions Architect - Associate SAA-C02 topic 1 question 216 discussion

A - DAX is a cache for read-intensive application, here the application is a read/write. B - multi az replication will increase the HA, but will not help in variable predictable load throughout the day. C - Autoscaling is the answer as per the documentation when the moring peak load is different from the load during the regular hour. https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/AutoScaling.html D - On Demand is for unpredictable workload, but here the workload is predictable. But still will work. https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.ReadWriteCapacityMode.html But as per the documentation we should go with C.

Answer C. Enable DynamoDB auto scaling when creating the tables. Traffic is predictable according to the scenario cost effective to enable autoscaling on tables. 'DynamoDB auto scaling reduces the unused capacity in the area between the provisioned and consumed capacity. improved ratio of consumed to provisioned capacity, which reduces the wasted overhead while providing sufficient operating capacity. With on-demand, DynamoDB instantly allocates capacity as it is needed. There is no concept of provisioned capacity, and there is no delay waiting for CloudWatch thresholds or the subsequent table updates. On-demand is ideal for bursty, new, or unpredictable workloads whose traffic can spike in seconds or minutes, and when underprovisioned capacity would impact the user experience. '

C is the answer

A Amazon DynamoDB Accelerator (DAX): A Read-Through/Write-Through Cache for DynamoDB As a read-through/write-through cache, DAX seamlessly intercepts the API calls that an application normally makes to DynamoDB so that both read and write activity are reflected in the DAX cache.

ANS: C

C https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/AutoScaling.html

Isn't autoscaling automatically enabled in dynamo db?

With DynamoDB Auto scaling, DynamoDB can automatically increase its write capacity for the spike and decrease the throughput after the spike.

C is the answer A is wrong as DAX is meant for caching B is wrong as Multi AZ replication would incur costs for sure; not cost effective D is wrong since C is definitely more cost effective

We will go for C because D is not right here as Traffic is predictable, not unpredictable....thats y.

Ans=C. Enable DynamoDB auto scaling when creating the tables.

Here there is a tie between C and D, however the actual tie breaker, in my opinion is "Cost effective" key words. Autoscaling can set an upper limit where on -demand has no upper limit. So I would go for C

And is C, D: On-Demand capacity - is 2.5 times more expensive and questions asks it to be cost effective

The choice between DynamoDB on-demand vs.DynamoDB auto scaling ... On-demand is good for small applications or for large applications with steep and unpredictable spikes that DynamoDB Auto Scaling cannot react to fast enough. For most other applications, provisioned capacity is likely a better option when factoring in cost. answer is "C"

D is correct Amazon DynamoDB on-demand is a flexible billing option capable of serving thousands of requests per second without capacity planning. DynamoDB on-demand offers pay-per-request pricing for read and write requests so that you pay only for what you use. When you choose on-demand mode, DynamoDB instantly accommodates your workloads as they ramp up or down to any previously reached traffic level. If a workload’s traffic level hits a new peak, DynamoDB adapts rapidly to accommodate the workload. Tables that use on-demand mode deliver the same single-digit millisecond latency, service-level agreement (SLA) commitment, and security that DynamoDB already offers. You can choose on-demand for both new and existing tables and you can continue using the existing DynamoDB APIs without changing code. On-demand mode is a good option if any of the following are true: You create new tables with unknown workloads. You have unpredictable application traffic. You prefer the ease of paying for only what you use.

My take- C, as it Variable & Predictable. If you have steady, predictable traffic, choose reserved capacity. Since you know you need a certain amount of capacity at all times, you can save from reduced rates. If you have variable, predictable traffic, choose provisioned capacity. Imagine you have significant traffic during the day but no traffic overnight. Reserved capacity would be wasted overnight, but your patterns are predictable enough that you could scale up your provisioned capacity when you need it. If you have variable, unpredictable traffic, choose on-demand. If your application gets random spikes, it can be hard to provision capacity to match demand. Use the on-demand feature so you don't throttle your users.

C for sure - https://www.serverless.com/blog/dynamodb-on-demand-serverless