DVA-C02 Development with AWS Services Practice Test 3 — 15 Questions

Question 1

A developer is creating a REST API using Amazon API Gateway with Lambda proxy integration. The API needs to accept and return binary data such as images or PDF files. The developer has configured the API to use the Lambda proxy integration. What additional configuration is required to support binary data?

Accepted Answer

In API Gateway, add the binary media types to the API settings, e.g., image/png, application/pdf.. With Lambda proxy integration, API Gateway passes the client request as-is to Lambda and returns the Lambda response as-is to the client. To handle binary data, you must explicitly declare the binary media types (e.g., image/png, application/pdf) in the API Gateway REST API settings. This tells API Gateway to base64-encode the binary payload before sending it to Lambda and to decode the base64-encoded response from Lambda back to binary for the client. Without this configuration, API Gateway treats all payloads as text and will corrupt binary data.

Answer

Set the Content-Type header to application/octet-stream in the Lambda response.

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Use an API Gateway custom domain with an SSL certificate.

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Enable API caching with binary support.

Question 2

A developer is building a REST API using Amazon API Gateway that will serve static content from an Amazon S3 bucket. The API should cache responses for frequently accessed objects to reduce latency. Which API Gateway feature should the developer enable?

Accepted Answer

API Gateway caching with TTL set per method.. API Gateway caching allows you to cache responses from your backend (e.g., an S3 bucket) for a specified Time-to-Live (TTL) per method, reducing the number of calls to the backend and lowering latency for frequently accessed objects. This feature is natively integrated with API Gateway and requires no additional services or complex configurations, making it the most direct solution for caching static content served through a REST API.

Answer

Amazon CloudFront as a custom domain.

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Lambda@Edge for caching.

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S3 Transfer Acceleration.

Question 3

A developer is building a serverless application using AWS SAM. The application includes a Lambda function that needs read-only access to an S3 bucket. The developer wants to use SAM's built-in policy templates to grant this permission. Which policy template should be used in the SAM template?

Accepted Answer

S3ReadPolicy. The S3ReadPolicy template is the correct choice because it grants read-only access to an S3 bucket, which aligns with the requirement for the Lambda function. AWS SAM provides this built-in IAM policy template to simplify attaching least-privilege permissions, specifically allowing s3:GetObject, s3:ListBucket, and similar read operations.

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S3CrudPolicy

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S3FullAccessPolicy

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S3StreamPolicy

Question 4

A developer is building a REST API using Amazon API Gateway and AWS Lambda. The API must support request validation, request throttling, and API keys. Which API Gateway feature should the developer use to enforce a daily request limit for each API key?

Accepted Answer

Usage plans. Usage plans in API Gateway allow you to set throttling and quota limits per API key, enabling daily request limits for each key. This feature is specifically designed to control usage by associating API keys with a plan that defines rate limits and quotas, such as a daily request cap. Option A is correct because it directly addresses the requirement to enforce a daily request limit per API key.

Answer

API keys

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Throttling settings at the method level

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AWS WAF

Question 5

A developer is creating a REST API using Amazon API Gateway and multiple AWS Lambda functions for different endpoints. The API must support CORS for a web application hosted on a different domain. The developer is using Lambda proxy integration. Which configuration is required to enable CORS?

Accepted Answer

Enable CORS in API Gateway and configure the Lambda functions to return the required CORS headers.. With Lambda proxy integration in API Gateway, the entire request and response are passed through to the Lambda function, which must return the HTTP response including status code, headers, and body. To enable CORS, the Lambda function must include the required CORS headers (e.g., Access-Control-Allow-Origin) in its response. While API Gateway can be configured to add CORS headers for non-proxy integrations, with proxy integration the Lambda function is solely responsible for returning all headers.

Answer

Configure API Gateway to return CORS headers and Lambda functions can ignore CORS.

Answer

Configure Lambda functions to return CORS headers and API Gateway will pass them through automatically.

Answer

Use a Lambda@Edge function at Amazon CloudFront to add CORS headers.

Question 6

A developer is building a microservices application composed of multiple AWS Lambda functions and an Amazon API Gateway. The developer needs to trace requests as they travel through different services to identify performance bottlenecks. Which AWS service should the developer integrate?

Accepted Answer

AWS X-Ray. AWS X-Ray is the correct service because it provides end-to-end tracing of requests as they travel through distributed applications, including AWS Lambda functions and API Gateway. It generates a service map that shows the flow of requests, latency breakdowns, and identifies performance bottlenecks across microservices. X-Ray integrates directly with Lambda and API Gateway via the X-Ray SDK and tracing headers, enabling trace propagation without code changes.

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AWS CloudTrail

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Amazon CloudWatch Logs

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Amazon Inspector

Question 7

An independent software vendor (ISV) is building a serverless application that processes incoming HTTP requests. The incoming requests must be validated against an OpenAPI schema before being passed to the Lambda function. Which AWS service should the ISV use to perform this validation?

Accepted Answer

Amazon API Gateway (with request validation). Amazon API Gateway's request validation feature can validate incoming HTTP requests against an OpenAPI (Swagger) schema before the request reaches the Lambda function. This offloads validation from the Lambda code, reducing cost and latency by rejecting invalid requests early. The ISV can define the schema in the API Gateway REST API or HTTP API, and API Gateway will automatically check headers, query strings, and request bodies against the schema.

Answer

AWS WAF

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Amazon Cognito

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AWS AppSync

Question 8

A developer is building a serverless web application using AWS Lambda and Amazon DynamoDB. The application needs to perform complex aggregations on data stored in DynamoDB. Which AWS service should the developer use to perform these aggregations efficiently without reading all the data into Lambda?

Accepted Answer

DynamoDB Streams with AWS Lambda. Option C is correct because DynamoDB Streams captures item-level changes in near real-time and can trigger a Lambda function to perform incremental aggregations without scanning the entire table. This pattern avoids reading all data into Lambda, making it efficient for continuous aggregation workloads.

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AWS Glue

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Amazon EMR

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Amazon Redshift

Question 9

A developer is building a serverless API using Amazon API Gateway and AWS Lambda. The API accepts JSON payloads in the request body. The developer wants to ensure that incoming requests have a valid structure before being passed to the Lambda function to reduce unnecessary invocations. Which API Gateway feature should the developer use?

Accepted Answer

Request validation using models and request validators. Option A is correct because API Gateway's request validation feature allows you to define a JSON Schema model for the request body and attach a request validator to the method. This validates the payload structure before the request reaches the Lambda function, preventing invalid payloads from triggering unnecessary invocations and reducing costs.

Answer

Usage plans with API keys

Answer

WAF (AWS WAF) integration

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Custom authorizer (Lambda authorizer)

Question 10

A developer is building a RESTful API using Amazon API Gateway. The API experiences high traffic spikes, and many requests are for the same data (e.g., a product catalog). The developer wants to reduce the load on the backend Lambda functions and improve response times for repeated requests. Which feature should the developer enable?

Accepted Answer

Enable API Gateway caching and set a TTL.. API Gateway caching stores responses from backend Lambda functions for a configurable time-to-live (TTL). When a request for the same data (e.g., a product catalog) arrives within the TTL period, API Gateway serves the cached response directly, reducing the number of invocations to the Lambda function and improving response latency. This directly addresses the need to reduce load on the backend and improve response times for repeated requests.

Answer

Use CloudFront with the API Gateway as an origin.

Answer

Enable throttling on the API Gateway usage plan.

Answer

Use a DynamoDB Accelerator (DAX) cluster for the backend database.

Question 11

A developer is building an application that needs to store session state data for a web application running on multiple EC2 instances behind an ALB. The data is ephemeral and should not persist if an instance is terminated. Which storage option should the developer use?

Accepted Answer

Amazon ElastiCache. Amazon ElastiCache is the correct choice because it provides a managed in-memory cache (e.g., Redis or Memcached) that is ideal for storing ephemeral session state data. Session data is temporary and must be shared across multiple EC2 instances behind an ALB, and ElastiCache offers sub-millisecond latency and automatic key expiration, ensuring data is not persisted if an instance terminates. This aligns with the requirement for non-persistent, high-performance session storage that survives individual instance failures.

Answer

Amazon RDS

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Amazon DynamoDB

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Amazon S3

Question 12

A developer is building a REST API using Amazon API Gateway and wants to transform the request data before sending it to the backend Lambda function. The transformation includes mapping query string parameters to a JSON body. Which API Gateway feature should be used?

Accepted Answer

Velocity Template Language (VTL) mapping templates. Option A is correct because API Gateway uses Velocity Template Language (VTL) mapping templates to transform incoming request data, such as mapping query string parameters into a JSON body before passing it to the backend Lambda function. This feature allows you to define a template that extracts values from the request's query string parameters (e.g., `$input.params('paramName')`) and constructs a new JSON payload, enabling seamless integration with Lambda without modifying the client request.

Answer

Lambda authorizer

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Request validator

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CORS configuration

Question 13

A developer is building a RESTful API using Amazon API Gateway and Lambda. The API should support CORS for a specific origin (https://example.com) and allow only GET and POST methods. Which configuration in the OPTIONS method response will satisfy these requirements?

Accepted Answer

Access-Control-Allow-Origin: https://example.com, Access-Control-Allow-Methods: GET,POST. Option A is correct because the OPTIONS method response must include the `Access-Control-Allow-Origin` header set to the specific origin `https://example.com` to restrict CORS access, and the `Access-Control-Allow-Methods` header must list only the allowed HTTP methods (`GET,POST`). The OPTIONS method itself is a preflight request and does not need to be listed in the allowed methods; it is automatically handled by the browser. This configuration satisfies the requirement of supporting CORS for a single origin and only GET and POST methods.

Answer

Access-Control-Allow-Origin: *, Access-Control-Allow-Methods: GET,POST,OPTIONS

Answer

Access-Control-Allow-Origin: https://example.com, Access-Control-Allow-Methods: GET,POST,OPTIONS

Answer

Access-Control-Allow-Origin: https://example.com, Access-Control-Allow-Headers: Content-Type

Question 14

A company wants to build a RESTful API that handles file uploads. The API needs to support multipart/form-data content type. The developer is using Amazon API Gateway and AWS Lambda. Which approach should the developer use to handle file uploads efficiently?

Accepted Answer

Use API Gateway to generate a presigned S3 URL, and have the client upload directly to S3. The Lambda function can then process the file asynchronously.. Option C is correct because it offloads the file upload to Amazon S3 directly via a presigned URL, which avoids the 10 MB payload limit and 29-second timeout of API Gateway and Lambda for large files. The client uploads the file to S3, and a separate Lambda function processes the file asynchronously, making the solution efficient and scalable for multipart/form-data uploads.

Answer

Configure API Gateway to pass the entire request body to Lambda, and process the file within the Lambda function.

Answer

Create a Lambda function that accepts the file and uploads it to S3 using the AWS SDK.

Answer

Use an EC2 instance to host a custom web server that accepts file uploads and writes to S3.

Question 15

A developer is building a web application that requires user authentication. The application will run on Amazon EC2 instances behind an Application Load Balancer. The developer wants to offload authentication to a managed service that supports social login providers. Which AWS service should the developer use?

Accepted Answer

Amazon Cognito. Amazon Cognito is the correct choice because it is a fully managed identity service designed for web and mobile applications, providing user authentication, authorization, and support for social login providers (e.g., Google, Facebook, Amazon) via OAuth 2.0 and OpenID Connect. It offloads the entire authentication workflow from the EC2 instances and ALB, integrating seamlessly with the ALB's authentication action to validate tokens before traffic reaches the application.

Answer

AWS Identity and Access Management (IAM)

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AWS Directory Service

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AWS Single Sign-On