Exam AWS Certified Solutions Architect - Professional topic 1 question 789 discussion

D. DAX accommodates unpredictable bursts of reading activity.

Throttling happens when the dynamodb table is scanned. "Read" is the issue here. I think DAX is the best solution here. Making the capacity "on demand" will solve the problem but not the cheapest solution.

Selected answer "A" To mitigate throttling in a cost-effective manner: Double the provisioned read capacity of the DynamoDB table Ensures sufficient capacity to handle increased workload caused by doubled Auto Scaling group Helps prevent throttling issues On-demand mode is not recommended due to its higher cost compared to provisioned capacity Duplicating the DynamoDB table and randomly selecting which table to access adds complexity and requires additional resources, making it an unsuitable solution Adding DynamoDB Accelerator (DAX) is unnecessary in this scenario DAX is a caching service that improves DynamoDB performance by caching frequently accessed data

What about B ? A double provision capacity for 100 request per second: 30.00 ( Upfront read cost (upfront):) usd / 12 monthes + 1.82 USD Monthly read cost (monthly) ~4 Usd D requires servers which will cost around 500 UDS for 3 large instance (for HA mode) C on demand mode per month for 100 request per second - 32 USD

C is the correct answer per the document explanation (see below). Reason: refer https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.ReadWriteCapacityMode.html section: Peak traffic and scaling properties If you need more than double your previous peak on table, DynamoDB automatically allocates more capacity as your traffic volume increases to help ensure that your workload does not experience throttling. However, throttling can occur if you exceed double your previous peak within 30 minutes. For example, if your application’s traffic pattern varies between 25,000 and 50,000 strongly consistent reads per second where 50,000 reads per second is the previously reached traffic peak, DynamoDB recommends spacing your traffic growth over at least 30 minutes before driving more than 100,000 reads per second.

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.

Its 100% C as per AWS documentation. Read <Peak traffic and scaling properties> section in below link https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.ReadWriteCapacityMode.html#HowItWorks.OnDemand

yeah i'd go for C as well. Several documents mention on demand mode as the way forward. there could still be queuing if data is not in cache when using DAX

"However, tables using the on-demand mode might still throttle." https://aws.amazon.com/premiumsupport/knowledge-center/on-demand-table-throttling-dynamodb/ Considering that switching on demand-mode might not solve the problem, i will go for DAX

I vote for DAX

Since its with peaks better to use on-demand and its more cost effective than to use DAX nodes and pay for them 24/7 - on-demand reads is 0.25$ for 1 million unit

Is On-Demand cheaper than DAX?

C. https://aws.amazon.com/premiumsupport/knowledge-center/on-demand-table-throttling-dynamodb/