- A
The S3 bucket policy blocks access from the API Gateway domain.
Why wrong: The S3 bucket policy controls access to S3 objects, not API Gateway requests. It cannot block requests to API Gateway, so this is not the cause.
- B
The S3 bucket is not configured for static website hosting.
Why wrong: If the website loads, the bucket is correctly configured for static hosting. This is not the cause of API call failures.
- C
The API Gateway API key is not included in the JavaScript code.
If the API Gateway endpoint requires an API key and the JavaScript code does not include it in the request headers, the API returns a 403 Forbidden error. This is the most likely cause.
- D
The S3 bucket does not have CORS configuration to allow cross-origin requests from the API Gateway domain.
Why wrong: CORS configuration for cross-origin requests should be enabled on API Gateway, not on S3. Missing CORS on API Gateway might cause issues, but the more common cause for 403 with API Gateway is a missing API key. Additionally, the option incorrectly states that S3 needs CORS.
S3 CORS Configuration: Allowing Cross-Origin Requests from API Gateway
This DVA-C02 practice question tests your understanding of development with aws services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: aPI Gateway API Key. 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 using Amazon S3 to host a static website. The website uses JavaScript to fetch data from an API Gateway endpoint. Users report that the website loads but API calls fail with HTTP 403 errors. The developer checks the S3 bucket policy and finds it allows public read access. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The API Gateway API key is not included in the JavaScript code.
The website loads from S3, but the API calls to API Gateway fail with 403. This is often due to missing API key. If the API Gateway endpoint requires an API key and the JavaScript code does not include it in the request headers, API Gateway returns a 403 Forbidden error. Option C is correct because the most likely cause is that the API key is not included in the JavaScript code, leading to the 403 response.
Key principle: API Gateway API Key
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The S3 bucket policy blocks access from the API Gateway domain.
Why it's wrong here
The S3 bucket policy controls access to S3 objects, not API Gateway requests. It cannot block requests to API Gateway, so this is not the cause.
- ✗
The S3 bucket is not configured for static website hosting.
Why it's wrong here
If the website loads, the bucket is correctly configured for static hosting. This is not the cause of API call failures.
- ✓
The API Gateway API key is not included in the JavaScript code.
Why this is correct
If the API Gateway endpoint requires an API key and the JavaScript code does not include it in the request headers, the API returns a 403 Forbidden error. This is the most likely cause.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
API Gateway API Key
- ✗
The S3 bucket does not have CORS configuration to allow cross-origin requests from the API Gateway domain.
Why it's wrong here
CORS configuration for cross-origin requests should be enabled on API Gateway, not on S3. Missing CORS on API Gateway might cause issues, but the more common cause for 403 with API Gateway is a missing API key. Additionally, the option incorrectly states that S3 needs CORS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often confuse CORS issues with API key requirements. While CORS can cause errors, a 403 Forbidden error from API Gateway often indicates that an API key is required but not provided. The trap is to assume it is a CORS problem without checking the API key requirement.
Detailed technical explanation
How to think about this question
Under the hood, when the browser makes a cross-origin XMLHttpRequest or fetch, it first sends a preflight OPTIONS request to the target server (API Gateway) to check for CORS headers like Access-Control-Allow-Origin. If the response lacks these headers, the browser blocks the actual request and surfaces a 403 in the console. In this scenario, the S3 bucket's CORS configuration must list the API Gateway domain as an allowed origin; otherwise, the browser never sends the GET/POST request to API Gateway, even though S3 itself is not involved in the API call.
KKey Concepts to Remember
- API Gateway API Key
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
API Gateway API Key
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.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
What to study next
Got this wrong? Here's your next step.
Review aPI Gateway API Key, then practise related DVA-C02 questions on the same topic to reinforce the concept.
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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 — API Gateway API Key.
What is the correct answer to this question?
The correct answer is: The API Gateway API key is not included in the JavaScript code. — The website loads from S3, but the API calls to API Gateway fail with 403. This is often due to missing API key. If the API Gateway endpoint requires an API key and the JavaScript code does not include it in the request headers, API Gateway returns a 403 Forbidden error. Option C is correct because the most likely cause is that the API key is not included in the JavaScript code, leading to the 403 response.
What should I do if I get this DVA-C02 question wrong?
Review aPI Gateway API Key, then practise related DVA-C02 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
API Gateway API Key
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Last reviewed: Jul 4, 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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