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Development with AWS Services →mediumMultiple ChoiceObjective-mapped

DVA-C02 Development with AWS Services Practice Question

This DVA-C02 practice question tests your understanding of development with aws services. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.

A developer is building a web application that uses Amazon DynamoDB as the database. The application needs to store user session data and must support eventual consistency reads for most use cases, but strongly consistent reads for critical operations. The developer wants to minimize costs. Which read capacity unit (RCU) configuration should the developer use?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

Question 1mediummultiple choice

Full question →

A
Use on-demand capacity mode to pay per request, avoiding provisioned capacity costs.
On-demand mode is ideal for unpredictable traffic and eliminates the overhead of capacity planning, often resulting in lower costs for variable workloads like session data.
B
Use provisioned capacity with 1 RCU per item, since eventually consistent reads consume half the RCUs.
Why wrong: The RCU consumption depends on item size, not a fixed '1 RCU per item'. Eventual consistency reads use 0.5 RCU per 4KB item, but this option inaccurately describes the cost.
C
Use provisioned capacity with sufficient RCUs to handle strongly consistent reads, as they consume the same as eventually consistent.
Why wrong: Strongly consistent reads consume twice the RCUs of eventually consistent reads (1 RCU per 4KB item vs. 0.5 RCU).
D
Use provisioned capacity with enough RCUs for peak traffic, and use DynamoDB Accelerator (DAX) for caching.
Why wrong: Adding DAX incurs additional costs, making it more expensive. The goal is to minimize costs, so on-demand is a better option.

Full breakdown with real-world context →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Use on-demand capacity mode to pay per request, avoiding provisioned capacity costs.

Option A is correct because on-demand capacity mode charges per request (read/write), eliminating the need to provision fixed RCUs. For a session store with mixed consistency requirements, on-demand is cost-effective when traffic is unpredictable or low, as you only pay for actual reads and writes. Eventually consistent reads consume half the RCUs of strongly consistent reads, but on-demand pricing automatically accounts for this difference without manual configuration.

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.

✓
Use on-demand capacity mode to pay per request, avoiding provisioned capacity costs.
Why this is correct
On-demand mode is ideal for unpredictable traffic and eliminates the overhead of capacity planning, often resulting in lower costs for variable workloads like session data.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use provisioned capacity with 1 RCU per item, since eventually consistent reads consume half the RCUs.
Why it's wrong here
The RCU consumption depends on item size, not a fixed '1 RCU per item'. Eventual consistency reads use 0.5 RCU per 4KB item, but this option inaccurately describes the cost.
✗
Use provisioned capacity with sufficient RCUs to handle strongly consistent reads, as they consume the same as eventually consistent.
Why it's wrong here
Strongly consistent reads consume twice the RCUs of eventually consistent reads (1 RCU per 4KB item vs. 0.5 RCU).
✗
Use provisioned capacity with enough RCUs for peak traffic, and use DynamoDB Accelerator (DAX) for caching.
Why it's wrong here
Adding DAX incurs additional costs, making it more expensive. The goal is to minimize costs, so on-demand is a better option.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates assume provisioned capacity is always cheaper, but for variable workloads like session stores, on-demand can minimize costs by eliminating unused capacity, especially when mixed consistency models are needed.

Detailed technical explanation

How to think about this question

Under the hood, DynamoDB on-demand mode uses a per-request pricing model where reads are billed in 4 KB increments for strongly consistent and 8 KB increments for eventually consistent (since eventually consistent reads are half the cost). For a session store, item sizes are typically small (e.g., 1–2 KB), so on-demand can be cheaper than over-provisioning for unpredictable traffic. A real-world scenario is a gaming leaderboard where session reads spike during tournaments; on-demand avoids wasted RCUs during idle periods.

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.

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FAQ

Questions learners often ask

What does this DVA-C02 question test?

Development with AWS Services — This question tests Development with AWS Services — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Use on-demand capacity mode to pay per request, avoiding provisioned capacity costs. — Option A is correct because on-demand capacity mode charges per request (read/write), eliminating the need to provision fixed RCUs. For a session store with mixed consistency requirements, on-demand is cost-effective when traffic is unpredictable or low, as you only pay for actual reads and writes. Eventually consistent reads consume half the RCUs of strongly consistent reads, but on-demand pricing automatically accounts for this difference without manual configuration.

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.

Are there clue words in this question I should notice?

Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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