The answer is using DynamoDB Auto Scaling and on-demand capacity mode for unpredictable workloads. Auto Scaling dynamically adjusts provisioned read and write capacity based on actual traffic, preventing the cost of over-provisioning during low-demand periods while still handling spikes. On-demand mode charges per request, making it ideal for unpredictable workloads where capacity planning is difficult, as it eliminates idle provisioned capacity costs entirely. On the AWS Certified Developer Associate DVA-C02 exam, this concept tests your understanding of DynamoDB cost optimization best practices, often appearing in scenario-based questions where you must choose between provisioned and on-demand based on traffic predictability. A common trap is selecting reserved capacity for variable workloads, but remember: if traffic is steady, use provisioned with Auto Scaling; if it’s erratic, go on-demand. Memory tip: “Steady scales, erratic on-demand.”
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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.
Which TWO practices help optimize costs in Amazon DynamoDB? (Choose 2.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Auto Scaling to adjust read/wapacity based on traffic.
Option B is correct because DynamoDB Auto Scaling automatically adjusts provisioned read and write capacity based on actual traffic patterns, preventing over-provisioning and reducing costs during low-demand periods. Option E is correct because on-demand capacity mode charges per request, making it cost-effective for unpredictable workloads where capacity planning is difficult, avoiding the cost of idle provisioned capacity.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Purchase reserved capacity for all tables regardless of usage.
Why it's wrong here
Reserved capacity is cost-effective only for predictable, steady workloads.
✓
Use Auto Scaling to adjust read/wapacity based on traffic.
Why this is correct
Auto scaling matches capacity to demand, reducing waste.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create multiple Global Secondary Indexes for query flexibility.
Why it's wrong here
GSIs increase storage and write costs.
✗
Enable DAX (DynamoDB Accelerator) for all tables.
Why it's wrong here
DAX incurs additional cost and is not always needed.
✓
Use on-demand capacity mode for unpredictable workloads.
Why this is correct
On-demand charges per request, avoiding unused capacity costs.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume more indexes or always-on DAX improve performance without considering the associated cost overhead, or they mistakenly think reserved capacity is always cheaper regardless of usage patterns.
Detailed technical explanation
How to think about this question
DynamoDB Auto Scaling uses the AWS Application Auto Scaling service to adjust provisioned capacity based on CloudWatch metrics (e.g., ConsumedWriteCapacityUnits), with target utilization (default 70%) to balance cost and performance. On-demand capacity mode uses a per-request pricing model (writes: $1.25 per million write request units, reads: $0.25 per million read request units) and can handle sudden spikes without throttling, but is typically more expensive than provisioned capacity for steady workloads. A real-world scenario: an e-commerce site with flash sales benefits from on-demand mode to avoid provisioning for peak traffic, while a logging system with predictable throughput uses Auto Scaling to minimize costs.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Auto Scaling to adjust read/wapacity based on traffic. — Option B is correct because DynamoDB Auto Scaling automatically adjusts provisioned read and write capacity based on actual traffic patterns, preventing over-provisioning and reducing costs during low-demand periods. Option E is correct because on-demand capacity mode charges per request, making it cost-effective for unpredictable workloads where capacity planning is difficult, avoiding the cost of idle provisioned capacity.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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