DVA-C02 VCE Exam Download

AWS AppConfig , a capability of AWS Systems Manager, is specifically designed to manage feature flags , configuration changes, and application toggles safely and dynamically. AWS documentation highlights AppConfig as the recommended service for enabling and disabling application features without redeploying code.

Feature flags in AppConfig allow developers to control visibility, rollout strategies, and gradual releases across environments. AppConfig supports validation, monitoring, and rollback to prevent misconfigurations from impacting users.

Option A is incorrect because AWS AppSync is a GraphQL service and does not manage feature flags. Options B and D misuse data storage and synchronization services for configuration management, introducing unnecessary complexity and risk.

Using AWS AppConfig enables developers to hide features , activate them instantly when ready, and manage them centrally with minimal operational overhead.

Therefore, AWS AppConfig feature flags are the correct and AWS-recommended solution.

The requirement is to test a new Lambda version without impacting the production API, and to do so with the least operational overhead. In API Gateway (REST API), the simplest pattern is to create a separate stage (for example, test) and use a stage variable to control which Lambda function version (or alias) the integration invokes.

With option B, the developer creates a new stage and defines a stage variable (commonly something like lambdaAlias or lambdaVersion). The API method integration URI can reference this stage variable so that each stage points to a different Lambda alias/version. The production stage (for example, prod) continues to call the stable version, while the test stage calls the new version. This cleanly isolates testing traffic and prevents any effect on the production REST API because stages have distinct invoke URLs and deployments.

This approach is operationally efficient because it avoids duplicating the API definition (new REST API) and avoids creating extra resources/methods that must be maintained. It also provides a repeatable process: future versions can be tested by updating only stage variables or alias routing rather than restructuring the API.

Why not the others:

A adds additional resources/methods and increases API surface area and maintenance.

C duplicates the entire API, increasing overhead and configuration drift risk.

D would impact production because it changes the integration used by the existing method.

Therefore, using a new stage + stage variables to route to the updated Lambda version meets the requirements with minimal overhead.

IAM Roles for EC2 (A): The most secure way to provide AWS permissions from EC2.

Create a role with a policy allowing s3:GetObject on the specific bucket.

Attach the role to an instance profile and associate that profile with your instances.

Pre-signed URLs (C): Temporary, authenticated URLs for specific S3 actions.

Modify the app to use the AWS SDK to call GeneratePresignedUrl.

Embed these URLs when a user is properly logged in, allowing download access.

To prove integrity (and authenticity) of data in transit, the correct cryptographic primitive is a digital signature. AWS KMS supports signing and verification operations using asymmetric KMS keys designed for signing (for example, RSA_SIGN_PSS, RSA_SIGN_PKCS1, or ECC_NIST_P256 key specs). The developer signs the data (or more commonly, a hash of the data) using the private key, and the external recipient verifies the signature using the corresponding public key. If the data is modified in transit, signature verification fails, proving the content was changed.

Option C exactly describes this model: sign with the private key, share the public key. The private key remains protected (ideally never leaving KMS). The public key can be distributed safely because it cannot be used to forge signatures.

Option A (encryption) provides confidentiality, not integrity proof to a third party, and sharing a symmetric encryption key is insecure and breaks key management principles.

Option B is incorrect because symmetric keys do not provide non-repudiation and generally require the verifier to possess the same secret key, which would allow the verifier to forge signatures too. While HMAC can validate integrity between trusted parties, it does not meet the typical “prove integrity” requirement to an external party without sharing a secret.

Option D is backward and insecure: you never share a private key.

Therefore, use an asymmetric KMS signing key to sign with the private key and provide the public key for verification.