- A
Enable CORS in API Gateway and ensure the OPTIONS method returns the required headers.
API Gateway must have CORS enabled, which automatically creates the OPTIONS method.
- B
Configure the Lambda function to return HTTP 200 for preflight OPTIONS requests.
Why wrong: Lambda does not directly handle preflight; API Gateway must handle it.
- C
Set the Access-Control-Allow-Origin header in the Lambda function response.
Why wrong: Lambda function can set headers but API Gateway must also be configured to pass them.
- D
Add the web application's domain to an API Gateway usage plan.
Why wrong: Usage plans control throttling, not CORS.
Question 927 of 1,616
API Gateway CORS Enable and Handle OPTIONS
This DVA-C02 practice question tests your understanding of development with aws services. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 using API Gateway to expose a Lambda function as a REST API. The API must be accessible from a web application hosted on a different domain. The developer configured CORS but the browser still shows CORS errors. What should the developer do to resolve the issue?
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 in API Gateway and ensure the OPTIONS method returns the required headers.
Option A is correct because enabling CORS in API Gateway automatically configures the OPTIONS method to return the required CORS headers (e.g., Access-Control-Allow-Origin, Access-Control-Allow-Methods) for preflight requests. This is the standard AWS approach to handle cross-origin requests from a browser, as the browser sends a preflight OPTIONS request before the actual request to check CORS permissions. The developer must ensure that the OPTIONS method is properly configured in API Gateway to respond with the necessary headers, which resolves the CORS error.
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 in API Gateway and ensure the OPTIONS method returns the required headers.
Why this is correct
API Gateway must have CORS enabled, which automatically creates the OPTIONS method.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure the Lambda function to return HTTP 200 for preflight OPTIONS requests.
Why it's wrong here
Lambda does not directly handle preflight; API Gateway must handle it.
- ✗
Set the Access-Control-Allow-Origin header in the Lambda function response.
Why it's wrong here
Lambda function can set headers but API Gateway must also be configured to pass them.
- ✗
Add the web application's domain to an API Gateway usage plan.
Why it's wrong here
Usage plans control throttling, not CORS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think setting CORS headers in the Lambda function response alone is sufficient, but they forget that the browser's preflight OPTIONS request must also be handled, which is why API Gateway's CORS configuration is essential.
Detailed technical explanation
How to think about this question
CORS (Cross-Origin Resource Sharing) is a W3C standard that uses HTTP headers to allow a server to indicate any origins other than its own from which a browser should permit loading resources. In API Gateway, enabling CORS automatically creates a mock OPTIONS endpoint that returns headers like Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers, which the browser checks during the preflight request. A common real-world scenario is when a web app hosted on a different domain (e.g., example.com) tries to call an API on api.example.com; without proper CORS configuration, the browser blocks the request even if the Lambda function returns the correct headers for the actual request.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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 in API Gateway and ensure the OPTIONS method returns the required headers. — Option A is correct because enabling CORS in API Gateway automatically configures the OPTIONS method to return the required CORS headers (e.g., Access-Control-Allow-Origin, Access-Control-Allow-Methods) for preflight requests. This is the standard AWS approach to handle cross-origin requests from a browser, as the browser sends a preflight OPTIONS request before the actual request to check CORS permissions. The developer must ensure that the OPTIONS method is properly configured in API Gateway to respond with the necessary headers, which resolves the CORS error.
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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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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