DVA-C02 Development with AWS Services Practice Test 11 — 15 Questions

Question 1

A developer is building a serverless application using AWS SAM. The application includes an Amazon API Gateway endpoint with a Lambda function that processes user uploads. The developer wants to enable API caching in the development stage to speed up repeated requests, but disable caching in the production stage. What is the most efficient way to achieve this?

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

Accepted Answer

Configure caching in the SAM template using the CacheClusterEnabled property and use CloudFormation conditions to enable it only in the dev stage.. AWS SAM extends AWS CloudFormation, allowing you to use CloudFormation conditions to conditionally enable the `CacheClusterEnabled` property on the `AWS::ApiGateway::Stage` resource. By defining a condition that evaluates to true only for the dev stage (e.g., based on a parameter like `StageName`), you can enable caching in dev and disable it in prod within a single SAM template, avoiding duplication and manual steps.

Answer

Create two separate SAM templates, one for dev with caching and one for prod without.

Answer

Enable caching in the API Gateway console after each deployment for the dev stage.

Answer

Use a custom CloudFormation resource to toggle caching based on a parameter.

Question 2

A developer is building a serverless application using AWS SAM. The application includes an Amazon API Gateway endpoint with a Lambda function that processes user uploads. The developer wants to enable API caching in the development stage to speed up repeated requests, but disable caching in the production stage. What is the most efficient way to achieve this?

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

Accepted Answer

Express Workflow. Express Workflows are designed for high-volume, short-duration (under 5 minutes) event-processing workloads, executing hundreds of thousands of state transitions per second with at-least-once semantics. Since the tasks are short-lived (under 30 seconds), run in parallel, and tolerate a small number of duplicate executions, Express Workflow is the correct choice because it offers lower cost and higher throughput than Standard Workflow, which guarantees exactly-once execution and is better suited for long-running, auditable workflows.

Answer

Standard Workflow

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AWS Lambda function with synchronous invocation

Answer

Amazon Simple Workflow Service (SWF)

Question 3

A developer is using the AWS Serverless Application Model (SAM) to define a serverless application with an API Gateway endpoint. The developer wants to enable API caching only in the development stage to speed up testing, but disable it in the production stage to ensure data freshness. What is the most efficient way to achieve this with SAM?

Accepted Answer

Use AWS SAM parameters with a condition to set CacheClusterEnabled based on the stage parameter.. AWS SAM parameters allow you to define a stage parameter (e.g., 'dev' or 'prod') and use a condition to conditionally set the `CacheClusterEnabled` property on the `AWS::Serverless::Api` resource. This is the most efficient approach because it uses a single template and SAM's built-in intrinsic functions (like `Fn::Equals`) to toggle caching based on the deployment stage, avoiding separate templates or post-deployment custom resources.

Answer

Deploy two separate SAM templates, one for each stage.

Answer

Use a custom resource to toggle caching after deployment.

Answer

Enable caching globally and configure a usage plan with a quota for production.

Question 4

A developer is building a serverless application using AWS SAM. The application includes an Amazon API Gateway endpoint with a Lambda function that processes user uploads. The developer wants to enable API caching in the development stage to speed up repeated requests, but disable caching in the production stage. What is the most efficient way to achieve this?

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

Accepted Answer

Define a SAM Parameter for the stage name, and reference it in the Lambda function's Environment property. AWS SAM allows you to define parameters (e.g., StageName) and reference them directly in the Lambda function's Environment property using CloudFormation intrinsic functions like !Ref. This enables dynamic injection of environment variables based on the deployment stage without modifying the template structure, aligning with Infrastructure as Code best practices for multi-environment deployments.

Answer

Use the Globals section of the SAM template to set environment variables

Answer

Hard-code the environment variables with different values in the template

Answer

Use an AWS Systems Manager Parameter Store parameter and reference it in the function

Question 5

A developer is building a RESTful API that allows clients to query a database and retrieve results. The backend logic is implemented in AWS Lambda, which queries an Amazon DynamoDB table. The developer wants to expose the API over HTTPS and manage authentication and throttling. Which AWS service should the developer use to create and manage the API endpoints?

Accepted Answer

Amazon API Gateway. Amazon API Gateway is the correct choice because it is a fully managed service that enables developers to create, publish, maintain, monitor, and secure RESTful APIs at any scale. It directly supports HTTPS endpoints, integrates natively with AWS Lambda for backend logic, and provides built-in features for authentication (e.g., IAM, Cognito, Lambda authorizers) and throttling (usage plans and rate limits). This makes it the ideal service for exposing a Lambda-backed DynamoDB query as a secure, managed API.

Answer

Application Load Balancer

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AWS CloudFront

Answer

Amazon S3

Question 6

A developer is building a serverless application using AWS SAM. The application includes an Amazon API Gateway endpoint with a Lambda function that processes user uploads. The developer wants to enable API caching in the development stage to speed up repeated requests, but disable caching in the production stage. What is the most efficient way to achieve this?

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

Accepted Answer

Store the object key and event ID in a DynamoDB table and check for duplicates before processing. Storing the S3 object key and event ID in a DynamoDB table with a TTL attribute allows the Lambda function to perform a conditional write (or check for an existing item) before processing. This ensures that even if duplicate S3 events are delivered (e.g., due to S3's at-least-once delivery guarantee), the same image is only processed once, achieving idempotency.

Answer

Set the Lambda function's concurrency to 1 to prevent concurrent executions

Answer

Use an Amazon SQS FIFO queue as the event destination

Answer

Enable S3 event notification filtering based on object size

Question 7

A developer is implementing an e-commerce application where a purchase operation must deduct inventory and create an order atomically. The inventory and orders are stored in separate DynamoDB tables. Which DynamoDB feature should the developer use to execute these operations as a single, all-or-nothing transaction?

Accepted Answer

DynamoDB Transactions. DynamoDB Transactions provide ACID (Atomicity, Consistency, Isolation, Durability) guarantees across one or more tables within a single AWS account and region. This allows the developer to combine the deduct-inventory and create-order operations into a single all-or-nothing transaction, ensuring that both succeed or both fail without partial updates.

Answer

DynamoDB Streams

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DynamoDB Accelerator (DAX)

Answer

DynamoDB Global Tables

Question 8

A developer is building a serverless application using AWS SAM. The application includes an Amazon API Gateway endpoint with a Lambda function that processes user uploads. The developer wants to enable API caching in the development stage to speed up repeated requests, but disable caching in the production stage. What is the most efficient way to achieve this?

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

Accepted Answer

Lambda proxy integration. Lambda proxy integration (option A) is correct because it automatically passes the entire HTTP request (method, headers, query parameters, path parameters) to the Lambda function as a single event object, allowing the same function to inspect the `httpMethod` field and branch logic for GET, POST, DELETE without any additional API Gateway mapping or transformation configuration. This minimizes both code (the function handles routing internally) and configuration (no need to define separate integration requests/responses per method).

Answer

Lambda custom integration

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HTTP integration

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Mock integration

Question 9

An application running on Amazon EC2 instances behind an Application Load Balancer (ALB) intermittently returns 503 errors. The ALB health checks are failing for some instances intermittently. The developer checks the instance system logs and finds no application errors. What is the most likely cause of the health check failures?

Accepted Answer

The application on the instances is experiencing resource exhaustion (e.g., memory or CPU) which causes it to stop responding to health checks temporarily. Intermittent 503 errors from the ALB combined with intermittent health check failures and no application errors in the system logs strongly point to transient resource exhaustion (CPU or memory) on the EC2 instances. When an instance runs out of memory or CPU, the application process may become unresponsive or be killed by the OS (e.g., OOM killer), causing it to fail health checks temporarily. Once resources are freed (e.g., after a spike subsides), the application resumes responding, which explains the intermittent nature of the failures.

Answer

The security group for the instances does not allow inbound traffic from the ALB on the health check port

Answer

The health check path is not configured correctly and the default path returns a 404 status

Answer

The target group is not configured with the correct protocol

Question 10

A company is building a RESTful API using Amazon API Gateway and AWS Lambda. The API must allow users to authenticate using an identity provider that supports OpenID Connect (OIDC). The developer wants to offload authentication and authorization to API Gateway. Which API Gateway feature should the developer use?

Accepted Answer

Native JWT authorizer (HTTP API). The Native JWT authorizer for HTTP APIs in API Gateway directly validates JSON Web Tokens (JWTs) from an OIDC-compliant identity provider without requiring custom code. This offloads both authentication and authorization to API Gateway by configuring the issuer URL and audience, matching the requirement to use an OIDC provider.

Answer

Amazon Cognito User Pools authorizer

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Custom Lambda authorizer

Answer

AWS IAM authorizer

Question 11

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.

Answer

Use an API Gateway custom domain with an SSL certificate.

Answer

Enable API caching with binary support.

Question 12

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.

Answer

Lambda@Edge for caching.

Answer

S3 Transfer Acceleration.

Question 13

A developer is building a serverless application using AWS SAM. The application includes an Amazon API Gateway endpoint with a Lambda function that processes user uploads. The developer wants to enable API caching in the development stage to speed up repeated requests, but disable caching in the production stage. What is the most efficient way to achieve this?

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

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.

Answer

S3CrudPolicy

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S3FullAccessPolicy

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S3StreamPolicy

Question 14

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

Answer

Throttling settings at the method level

Answer

AWS WAF

Question 15

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.