- A
Enable CORS on the API Gateway resource using the 'Enable CORS' feature in the API Gateway console, which adds the OPTIONS method and appropriate headers.
API Gateway's built-in CORS feature automatically configures the OPTIONS method and adds the necessary headers (Access-Control-Allow-Origin, etc.) to the method responses and integration responses.
- B
In the Lambda function code, add the 'Access-Control-Allow-Origin' header to every response.
Why wrong: While adding CORS headers in Lambda is necessary, it alone is not sufficient. The browser sends a preflight OPTIONS request that must be handled by API Gateway before the Lambda is invoked. Without an OPTIONS method configured, the preflight will fail.
- C
Configure Amazon CloudFront in front of API Gateway to handle CORS.
Why wrong: CloudFront can forward CORS headers, but it does not replace the need to configure CORS on the API Gateway itself. This adds unnecessary complexity.
- D
Set a bucket policy on the S3 bucket that hosts the web application to allow cross-origin requests.
Why wrong: Bucket policies are used to control access to S3 resources. They do not affect CORS behavior for API Gateway.
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 serverless REST API using Amazon API Gateway and AWS Lambda. The API will be consumed by a web application hosted on a different domain. The developer needs to enable Cross-Origin Resource Sharing (CORS) for all HTTP methods. What is the most efficient way to achieve this?
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
Enable CORS on the API Gateway resource using the 'Enable CORS' feature in the API Gateway console, which adds the OPTIONS method and appropriate headers.
Option A is correct because API Gateway's 'Enable CORS' feature automatically creates an OPTIONS method for the selected resource and configures the necessary response headers (e.g., Access-Control-Allow-Origin, Access-Control-Allow-Methods, Access-Control-Allow-Headers) to handle preflight requests. This is the most efficient approach as it centralizes CORS configuration at the API Gateway layer, eliminating the need for manual header management in Lambda or additional infrastructure.
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.
- ✓
Enable CORS on the API Gateway resource using the 'Enable CORS' feature in the API Gateway console, which adds the OPTIONS method and appropriate headers.
Why this is correct
API Gateway's built-in CORS feature automatically configures the OPTIONS method and adds the necessary headers (Access-Control-Allow-Origin, etc.) to the method responses and integration responses.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
In the Lambda function code, add the 'Access-Control-Allow-Origin' header to every response.
Why it's wrong here
While adding CORS headers in Lambda is necessary, it alone is not sufficient. The browser sends a preflight OPTIONS request that must be handled by API Gateway before the Lambda is invoked. Without an OPTIONS method configured, the preflight will fail.
- ✗
Configure Amazon CloudFront in front of API Gateway to handle CORS.
Why it's wrong here
CloudFront can forward CORS headers, but it does not replace the need to configure CORS on the API Gateway itself. This adds unnecessary complexity.
- ✗
Set a bucket policy on the S3 bucket that hosts the web application to allow cross-origin requests.
Why it's wrong here
Bucket policies are used to control access to S3 resources. They do not affect CORS behavior for API Gateway.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume adding CORS headers only in the Lambda function code is sufficient, overlooking the mandatory preflight OPTIONS request that API Gateway must handle separately.
Detailed technical explanation
How to think about this question
CORS is enforced by the browser, not the server, and requires the server to respond to preflight OPTIONS requests with specific headers like Access-Control-Allow-Origin (which can be a specific domain or '*'). API Gateway's 'Enable CORS' feature automatically generates the OPTIONS method and maps headers from integration responses, but developers must also ensure that the actual Lambda response includes the Access-Control-Allow-Origin header for non-preflight requests. A common pitfall is forgetting that CORS headers must be present in both the OPTIONS response (preflight) and the actual response (e.g., GET, POST), which is why a combined approach (API Gateway for preflight, Lambda for actual responses) is often needed.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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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: Enable CORS on the API Gateway resource using the 'Enable CORS' feature in the API Gateway console, which adds the OPTIONS method and appropriate headers. — Option A is correct because API Gateway's 'Enable CORS' feature automatically creates an OPTIONS method for the selected resource and configures the necessary response headers (e.g., Access-Control-Allow-Origin, Access-Control-Allow-Methods, Access-Control-Allow-Headers) to handle preflight requests. This is the most efficient approach as it centralizes CORS configuration at the API Gateway layer, eliminating the need for manual header management in Lambda or additional infrastructure.
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.
About these practice questions
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Last reviewed: Jun 11, 2026
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.
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