DVA-C02 Development with AWS Services Practice Test 12 — 15 Questions

Question 1

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?

Choose an answer to begin — your selection is scored in the full session.

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 2

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. 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 3

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. 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.

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Usage plans with API keys

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WAF (AWS WAF) integration

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Custom authorizer (Lambda authorizer)

Question 4

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.

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Use CloudFront with the API Gateway as an origin.

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Enable throttling on the API Gateway usage plan.

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

Question 5

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. 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.

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Lambda authorizer

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Request validator

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CORS configuration

Question 6

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. 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.

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

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

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

Question 7

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.. 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.

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

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

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

Question 8

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.

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AWS Identity and Access Management (IAM)

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AWS Directory Service

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AWS Single Sign-On

Question 9

A developer is using Amazon API Gateway with a Lambda authorizer to control access to an API. The authorizer function needs to decode a JWT token from the request header and return an IAM policy. Which type of Lambda authorizer should be used?

Accepted Answer

TOKEN authorizer with the token passed in the Authorization header.. A TOKEN authorizer is designed to receive a JWT or OAuth token in the Authorization header and pass it directly to the Lambda function for validation. The Lambda function then decodes the token and returns an IAM policy document to allow or deny the API request. This is the correct choice because the question explicitly states the token is in the request header and needs to be decoded, which matches the TOKEN authorizer's behavior of forwarding the raw token value.

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REQUEST authorizer with the token in a custom header.

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Use Amazon Cognito User Pools as the authorizer.

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Use a resource policy to allow or deny access based on the JWT token.

Question 10

A developer is building a serverless application that needs to process messages from an Amazon SQS queue and store the results in an Amazon DynamoDB table. Which AWS service should the developer use to orchestrate the processing logic without managing servers?

Accepted Answer

AWS Lambda. AWS Lambda is the correct choice because it is a serverless compute service that can be triggered by SQS messages via event source mappings, process each message, and write results to DynamoDB without provisioning or managing any servers. The developer simply uploads the processing code, and Lambda handles scaling, concurrency, and execution, making it ideal for this event-driven, serverless workflow.

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Amazon Elastic Container Service (ECS) with Fargate

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Amazon EC2 instances with a custom application

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AWS Step Functions

Question 11

A developer is building a REST API using Amazon API Gateway and wants to validate the incoming request body against a JSON schema before passing the request to the backend Lambda function. Which API Gateway feature should the developer use?

Accepted Answer

Request validation. API Gateway's request validation feature allows you to define a JSON schema (using JSON Schema Draft 4) for the request body and automatically reject requests that do not conform before they reach the backend. This offloads validation from the Lambda function, reducing cold start overhead and ensuring only valid payloads are processed. The developer can configure this in the API Gateway console or via the OpenAPI specification.

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Mapping templates

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Integration request

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Stage variables

Question 12

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?

Accepted Answer

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 '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.

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In the Lambda function code, add the 'Access-Control-Allow-Origin' header to every response.

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Configure Amazon CloudFront in front of API Gateway to handle CORS.

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Set a bucket policy on the S3 bucket that hosts the web application to allow cross-origin requests.

Question 13

A developer has an Amazon S3 bucket containing private user documents. The application must generate a time-limited URL for users to download their own documents without requiring the users to have AWS credentials. Which solution should the developer use?

Accepted Answer

Create a pre-signed URL for each object using the AWS SDK with an appropriate expiration time.. Pre-signed URLs allow temporary, time-limited access to private S3 objects without requiring the user to have AWS credentials. The developer generates the URL server-side using the AWS SDK, embedding an expiration time, and the user can download the object directly via HTTP GET. This meets the requirement of granting ephemeral access to specific documents for unauthenticated users.

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Use CloudFront signed URLs with an origin access identity (OAI) to restrict access to the S3 bucket.

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Set a bucket policy that allows public read access for the specific users based on their IP addresses.

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Provide the users with IAM user credentials that have read access to the bucket.

Question 14

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?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Standard queue. Amazon SQS Standard queues provide at-least-once delivery and best-effort ordering, making them ideal for microservices that can tolerate duplicate messages and do not require strict message sequencing. Since the application processes events from multiple sources and message ordering is not important, a Standard queue meets the requirements without the throughput limitations of FIFO queues.

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FIFO queue

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Dead-letter queue

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Delay queue

Question 15

A developer is building an AWS Lambda function that needs to retrieve a database password securely. The password is stored in AWS Secrets Manager and is rotated every 30 days. The function must minimize the number of API calls to Secrets Manager. Which approach should the developer use?

Accepted Answer

Retrieve the secret from Secrets Manager once outside the handler function, cache it in a global variable, and refresh the cache if the secret fails.. It retrieves the secret once during the Lambda cold start (outside the handler), caches it in a global variable, and only refreshes the cache if the secret fails (e.g., due to rotation). This minimizes API calls to Secrets Manager while still handling secret rotation gracefully, as the cached secret remains valid until a failure occurs.

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Store the database password as an encrypted environment variable in the Lambda function.

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Call Secrets Manager on every invocation to get the latest secret.

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Use AWS Systems Manager Parameter Store SecureString instead of Secrets Manager.