DVA-C02 Development with AWS Services Practice Question
This DVA-C02 practice question tests your understanding of development with aws services. 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.
A Lambda function writes order records to DynamoDB after receiving API Gateway requests. Which two practices improve reliability during client retries?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use an idempotency token from the request in a conditional DynamoDB write
Option A is correct because using an idempotency token from the request in a conditional DynamoDB write ensures that if a client retries the same request, the Lambda function can check whether the token already exists in the table. If it does, the write is skipped, preventing duplicate order records. This pattern leverages DynamoDB's conditional writes (e.g., `attribute_not_exists(idempotencyKey)`) to guarantee exactly-once processing, which is critical for reliability during retries.
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 an idempotency token from the request in a conditional DynamoDB write
Why this is correct
Correct for the stated requirement.
Related concept
Read the scenario before looking for a memorised answer.
✗
Generate a new random primary key for every retry
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
✓
Return the same result for repeated requests with the same idempotency key
Why this is correct
Correct for the stated requirement.
Related concept
Read the scenario before looking for a memorised answer.
✗
Disable API Gateway request validation
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse idempotency with uniqueness — they might think generating a new random key (Option B) is a valid retry strategy, but it actually creates duplicates, whereas the correct approach is to reuse the same token and conditionally reject duplicates.
Detailed technical explanation
How to think about this question
Under the hood, DynamoDB conditional writes use the `ConditionExpression` parameter to evaluate an expression before performing the write; if the condition fails (e.g., the idempotency key already exists), the write is rejected with a `ConditionalCheckFailedException`. This mechanism relies on DynamoDB's internal locking and atomicity, making it safe for concurrent retries. In a real-world scenario, the idempotency token is often derived from a request header (e.g., `Idempotency-Key`) and stored with a TTL attribute to automatically expire stale tokens, balancing reliability with storage 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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
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 an idempotency token from the request in a conditional DynamoDB write — Option A is correct because using an idempotency token from the request in a conditional DynamoDB write ensures that if a client retries the same request, the Lambda function can check whether the token already exists in the table. If it does, the write is skipped, preventing duplicate order records. This pattern leverages DynamoDB's conditional writes (e.g., `attribute_not_exists(idempotencyKey)`) to guarantee exactly-once processing, which is critical for reliability during retries.
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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This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.
Question Discussion
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