DVA-C02 Practice Test 10 — 10 Questions

Question 1

A developer is using Amazon API Gateway to create a REST API. The API must support CORS (Cross-Origin Resource Sharing) to allow requests from a web application hosted on a different domain. What must the developer do to enable CORS?

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

Accepted Answer

Enable CORS in the API Gateway settings and configure the required headers.. Enabling CORS in API Gateway requires explicit configuration: you must enable CORS on the API Gateway resource, which automatically generates an OPTIONS method and adds the necessary CORS headers (Access-Control-Allow-Origin, Access-Control-Allow-Methods, Access-Control-Allow-Headers) to responses. This is done through the API Gateway console or API configuration, not by the backend Lambda function or CloudFront.

Answer

Use Amazon CloudFront to proxy the API and add CORS headers.

Answer

Nothing; API Gateway automatically handles CORS.

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Add CORS headers in the Lambda function code.

Question 2

A developer wants to debug an AWS Lambda function by viewing real-time logs. Which AWS service should the developer use?

Accepted Answer

Amazon CloudWatch Logs. Amazon CloudWatch Logs is the correct service because AWS Lambda automatically streams all execution logs, including real-time output from console.log() statements and any errors, to CloudWatch Logs. The developer can use the CloudWatch Logs console or the `aws logs tail` command to view these logs in near real-time, enabling effective debugging of function behavior as it executes.

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AWS X-Ray

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Amazon S3

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AWS CloudTrail

Question 3

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.

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DynamoDB Streams

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DynamoDB Accelerator (DAX)

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DynamoDB Global Tables

Question 4

A developer is using Amazon DynamoDB to store session data for a web application. The application reads and writes a single item per user session. The traffic pattern shows occasional spikes. The developer wants to minimize read and write costs. Which DynamoDB capacity mode should the developer choose?

Accepted Answer

On-demand capacity. On-demand capacity mode is ideal for unpredictable traffic patterns with occasional spikes because it automatically scales read and write throughput based on actual usage, charging only for consumed operations. Since the application reads and writes a single item per session and experiences spikes, on-demand eliminates the need to provision for peak capacity, minimizing costs compared to over-provisioning.

Answer

Reserved capacity

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Provisioned capacity with manual scaling

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Provisioned capacity with auto scaling

Question 5

A developer is deploying a microservices architecture on Amazon ECS using Fargate launch type. The services need to communicate with each other. The developer wants to use service discovery so that services can find each other by name. Which AWS service should the developer use?

Accepted Answer

AWS Cloud Map. AWS Cloud Map is the correct choice because it is a cloud resource discovery service that allows microservices to register their DNS names and health checks, enabling dynamic service discovery. With Amazon ECS and Fargate, services can use AWS Cloud Map namespaces (either API-based or DNS-based) to resolve each other by logical service names, which is essential for inter-service communication in a microservices architecture.

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Amazon Route 53 private hosted zones

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Amazon ECR

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Application Load Balancer

Question 6

A developer is using AWS Elastic Beanstalk to deploy a Node.js application. The developer wants to run a custom script to set environment variables before the application starts. Which configuration file and location should the developer use?

Accepted Answer

Add a configuration file in the .ebextensions directory that uses container_commands.. `.ebextensions` configuration files with `container_commands` allow you to run custom commands before the application starts. `container_commands` execute after the application and web server have been set up but before the application is deployed, making them ideal for setting environment variables or running setup scripts. The files must be in YAML or JSON format and placed in the `.ebextensions` directory at the root of your source bundle.

Answer

Add a Procfile to the application root.

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Place a shell script in the .ebextensions/scripts directory.

Answer

Add a cron.yaml file to the .ebextensions directory.

Question 7

A developer has written an AWS Lambda function that processes messages from an Amazon SQS queue. The function is configured with a reserved concurrency of 5. The SQS queue has 10,000 messages waiting to be processed. What will happen when the Lambda function is invoked?

Accepted Answer

Lambda will process messages with a maximum of 5 concurrent executions, each processing a batch of messages.. AWS Lambda integrates with Amazon SQS to poll the queue and invoke the function with batches of messages. The reserved concurrency of 5 caps the maximum number of concurrent executions, so Lambda will process messages with up to 5 concurrent invocations, each receiving a batch of up to 10 messages (default batch size). The remaining messages remain in the queue until they are processed or the visibility timeout expires.

Answer

Lambda will automatically increase reserved concurrency to handle the load.

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Lambda will reject the invocation because reserved concurrency is too low.

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Lambda will scale up to 20 concurrent executions to process all messages quickly.

Question 8

A company uses AWS CodePipeline with a manual approval step before deployment. The developer wants to ensure that if a pipeline execution is waiting for approval and new code is pushed, the awaiting execution is canceled and a new one starts with the latest code. Which pipeline execution mode should be configured?

Accepted Answer

Superseded. The Superseded execution mode is correct because it automatically cancels any currently running or waiting pipeline execution when a new one is triggered, ensuring that only the latest code proceeds through the pipeline. This is ideal for scenarios with manual approval steps where stale executions should not block or delay the deployment of the most recent commit.

Answer

Queued

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Parallel

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Single

Question 9

A developer is deploying a Node.js application on AWS Elastic Beanstalk. The application uses environment variables for database credentials. The developer wants to ensure that the credentials are encrypted at rest and rotated automatically. Which solution meets these requirements with minimal effort?

Accepted Answer

Store the credentials in AWS Secrets Manager and retrieve them in the application code. Configure automatic rotation.. AWS Secrets Manager is the correct choice because it provides built-in automatic rotation of secrets (including database credentials) with minimal configuration, and it encrypts secrets at rest using AWS KMS. The developer can retrieve the credentials at runtime via the AWS SDK, avoiding hardcoding or plaintext exposure. Elastic Beanstalk environment properties do not offer encryption at rest or rotation, and while Parameter Store SecureString parameters encrypt at rest, they lack native automatic rotation without additional custom logic.

Answer

Hardcode the credentials in the application code and use environment variables for different environments.

Answer

Store the credentials in AWS Systems Manager Parameter Store as SecureString parameters and reference them in the application code.

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Use Elastic Beanstalk environment properties to set the credentials as plaintext environment variables.

Question 10

A developer is deploying a web application on AWS Elastic Beanstalk. The application needs to run on multiple instances behind a load balancer. Which deployment policy will cause the LEAST downtime?

Accepted Answer

Rolling with additional batch. Rolling with additional batch (C) is the correct deployment policy for minimizing downtime because it first launches a full new batch of instances in addition to the existing ones, then shifts traffic to the new instances before terminating the old ones. This ensures that the full capacity remains available throughout the deployment, unlike other policies that temporarily reduce capacity or require a full replacement.

Answer

All at once

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Rolling

Answer

Immutable