SOA-C02 Cost and Performance Optimization Practice Question
This SOA-C02 practice question tests your understanding of cost and performance optimization. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: provisioned capacity allows setting specific RCU/WCU for DynamoDB tables.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company uses an Amazon DynamoDB table with on-demand capacity mode. The table handles a workload with a steady baseline of 500 writes per second but spikes to 2,000 writes per second for a few hours each day. The SysOps administrator wants to reduce costs without affecting application performance during spikes. Which action should the administrator take?
Switch to provisioned capacity with auto scaling to handle the spikes.
Provisioned capacity with auto scaling can be more cost-effective for workloads with a predictable baseline and occasional spikes. You pay only for the provisioned capacity, not per-request.
B
Enable DynamoDB Accelerator (DAX) to cache reads.
Why wrong: DAX is a read cache; it does not reduce write capacity costs.
C
Create a global table to distribute write traffic.
Why wrong: Global tables replicate data across regions and increase write costs due to additional replication.
D
Use Amazon ElastiCache to buffer write requests.
Why wrong: ElastiCache is not integrated with DynamoDB write capacity and does not reduce the cost of writes.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Switch to provisioned capacity with auto scaling to handle the spikes.
On-demand capacity mode is ideal for unpredictable workloads but costs more per write than provisioned capacity. Since this workload has a predictable baseline and spikes, switching to provisioned capacity with auto scaling allows you to pay a lower rate for the steady 500 writes per second while auto scaling automatically adds capacity to handle the 2,000 writes per second spikes, reducing overall cost without impacting performance.
Key principle: Provisioned capacity allows setting specific RCU/WCU for DynamoDB tables.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Switch to provisioned capacity with auto scaling to handle the spikes.
Why this is correct
Provisioned capacity with auto scaling can be more cost-effective for workloads with a predictable baseline and occasional spikes. You pay only for the provisioned capacity, not per-request.
Related concept
Provisioned capacity allows setting specific RCU/WCU for DynamoDB tables.
✗
Enable DynamoDB Accelerator (DAX) to cache reads.
Why it's wrong here
DAX is a read cache; it does not reduce write capacity costs.
✗
Create a global table to distribute write traffic.
Why it's wrong here
Global tables replicate data across regions and increase write costs due to additional replication.
✗
Use Amazon ElastiCache to buffer write requests.
Why it's wrong here
ElastiCache is not integrated with DynamoDB write capacity and does not reduce the cost of writes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume on-demand is always the cheapest for spiky workloads, but the question specifies a predictable spike pattern, making provisioned with auto scaling more cost-effective; also, candidates may confuse DAX (read cache) with a write optimization tool.
Detailed technical explanation
How to think about this question
Provisioned capacity with auto scaling uses the AWS Application Auto Scaling service to adjust the table's write capacity units (WCUs) based on a target utilization (default 70%). During spikes, auto scaling can increase capacity up to a configured maximum, but it may take a few minutes to scale out, so setting a higher minimum capacity or using a burst buffer (e.g., DynamoDB write sharding) can prevent throttling. On-demand mode charges per write request unit (WRU) at a higher rate (about 1.25x the provisioned rate), so predictable workloads benefit from provisioned pricing.
KKey Concepts to Remember
Provisioned capacity allows setting specific RCU/WCU for DynamoDB tables.
Auto scaling for provisioned capacity dynamically adjusts WCUs based on actual usage.
On-demand capacity is pay-per-request, suitable for unpredictable workloads.
Provisioned capacity with auto scaling is often more cost-effective for predictable baselines with spikes.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Provisioned capacity allows setting specific RCU/WCU for DynamoDB tables.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Review provisioned capacity allows setting specific RCU/WCU for DynamoDB tables., then practise related SOA-C02 questions on the same topic to reinforce the concept.
Cost and Performance Optimization — This question tests Cost and Performance Optimization — Provisioned capacity allows setting specific RCU/WCU for DynamoDB tables..
What is the correct answer to this question?
The correct answer is: Switch to provisioned capacity with auto scaling to handle the spikes. — On-demand capacity mode is ideal for unpredictable workloads but costs more per write than provisioned capacity. Since this workload has a predictable baseline and spikes, switching to provisioned capacity with auto scaling allows you to pay a lower rate for the steady 500 writes per second while auto scaling automatically adds capacity to handle the 2,000 writes per second spikes, reducing overall cost without impacting performance.
What should I do if I get this SOA-C02 question wrong?
Review provisioned capacity allows setting specific RCU/WCU for DynamoDB tables., then practise related SOA-C02 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Provisioned capacity allows setting specific RCU/WCU for DynamoDB tables.
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Question Discussion
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