DVA-C02 Mock Exam 86 — 25 Questions

Question 1

A company uses AWS CodeBuild to run tests and build artifacts for a Java application. The build process is taking longer than expected. The developer wants to speed up the build by caching dependencies. What should the developer do?

Accepted Answer

Enable local caching in the CodeBuild project configuration.. Option C is correct because CodeBuild's local caching feature allows the build environment to cache dependencies (e.g., Maven local repository) in a local directory that persists across build runs for the same project. This eliminates the need to re-download dependencies on every build, significantly reducing build time. The cache is stored on the build instance's local storage and is automatically managed by CodeBuild.

Answer

Use a CodeCommit repository to store dependencies.

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Store dependencies in an S3 bucket and download them in each build.

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Mount an Amazon EFS file system to the build environment and store dependencies there.

Question 2

A developer is using AWS OpsWorks for Chef Automate to manage a stack. The developer needs to deploy a new application version to existing instances. Which OpsWorks feature should the developer use?

Accepted Answer

Recipes. Recipes are Chef cookbook components that define the sequence of commands to execute on an instance. To deploy a new application version, the developer can run a custom recipe (e.g., via an OpsWorks lifecycle event or a manual 'Execute Recipes' action) that pulls the updated code, restarts services, or performs any necessary deployment steps. This directly maps to the requirement of deploying a new version to existing instances.

Answer

Custom JSON

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Stacks

Answer

Layers

Question 3

A company uses AWS CodePipeline with CodeBuild and CodeDeploy. The pipeline deploys a web application to an Auto Scaling group. Recently, a deployment failed because the build output exceeded the CodeDeploy deployment limit for the number of files. The developer needs to prevent this issue in the future. What should the developer do?

Accepted Answer

Store the build output in an S3 bucket and modify the CodeDeploy deployment to pull the archive from S3.. Option C is correct because CodeDeploy has a hard limit on the number of files in a deployment archive (currently 10,000 files for in-place deployments). By storing the build output in an S3 bucket and configuring CodeDeploy to pull the archive from S3, the developer bypasses the file count limit entirely. S3 has no such file count restriction, and CodeDeploy can retrieve the archive directly, allowing deployments with a large number of files to succeed.

Answer

Use AWS CodeStar to manage the pipeline.

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Increase the instance size in the Auto Scaling group to handle more files.

Answer

Modify the buildspec.yml to compress the build output.

Question 4

A developer is deploying a microservices application on Amazon ECS using Fargate. The application uses an Application Load Balancer (ALB) to distribute traffic. The developer needs to perform a blue/green deployment with automatic rollback if health checks fail. What should the developer use?

Accepted Answer

Use AWS CodeDeploy with a blue/green deployment configuration.. AWS CodeDeploy natively supports blue/green deployments for Amazon ECS, allowing you to specify a blue/green configuration that automatically shifts traffic from the old (blue) task set to the new (green) task set. It integrates with the ALB to perform health checks and can automatically roll back the deployment if the health checks fail, meeting the requirement without manual intervention.

Answer

Configure ECS service auto scaling to replace tasks gradually.

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Manually update the ECS service using the AWS Management Console.

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Use AWS CloudFormation to update the ECS service with a new task definition.

Question 5

A developer is deploying a microservice to Amazon ECS using Fargate. The service needs to be accessible from the internet via an Application Load Balancer. The developer creates the ECS service with a network load balancer by mistake. What is the minimal change required to fix the deployment?

Accepted Answer

Create a new target group for the ALB and update the ECS service to use it.. The minimal change is to create a new target group configured for the Application Load Balancer (ALB) and update the ECS service to use it. An ECS service with Fargate must be associated with a target group that matches the load balancer type; since the service was created with a Network Load Balancer (NLB), its existing target group uses TCP/TLS protocols. Creating an ALB-compatible target group (HTTP/HTTPS) and reassigning it to the service corrects the mismatch without deleting the service.

Answer

Update the ECS service to point to the ALB listener.

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Change the existing target group to use ALB protocol.

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Delete the ECS service and recreate it with an ALB.

Question 6

A company uses AWS Elastic Beanstalk to deploy a web application. The environment is currently running a previous version. The developer uploads a new application version and deploys it to the environment. After the deployment, the environment health status turns 'Severe' and the new version is not accessible. The developer needs to quickly revert to the previous working version. What should the developer do?

Accepted Answer

Use the Elastic Beanstalk console to deploy the previous application version.. Option B is correct because Elastic Beanstalk allows you to deploy a previous application version directly from the console or CLI without creating a new environment. This action replaces the current application version in the existing environment, restoring the previously working code and resolving the health status. It is the fastest and most straightforward way to revert while preserving the environment's configuration and resources.

Answer

Create a new environment with the previous version and swap CNAMEs.

Answer

Roll back the environment configuration to a previous saved configuration.

Answer

Terminate the environment and launch a new one with the previous version.

Question 7

A company deploys a serverless application using AWS SAM. The application includes an API Gateway REST API and multiple Lambda functions. The developer wants to deploy a new version of the API with a canary release strategy, sending 10% of traffic to the new version initially. Which SAM template configuration should the developer use?

Accepted Answer

Set Type: Canary in the DeploymentPreference of the Lambda function and add CanarySetting: { Percent: 10 } under DeploymentPreference.. Option A is correct because AWS SAM's `DeploymentPreference` with `Type: Canary` on the Lambda function enables canary traffic shifting for the API Gateway integration. The `CanarySetting` property with `Percent: 10` specifies that 10% of traffic is initially routed to the new Lambda version, while the remaining 90% goes to the previous version. This configuration leverages SAM's built-in CodeDeploy integration to manage the canary release automatically.

Answer

Set CanarySetting: { Percent: 10 } in the API Gateway resource's properties.

Answer

Set Type: Canary and TrafficShiftType: Canary in the DeploymentPreference of the Lambda function.

Answer

Set Type: Canary in the DeploymentPreference of the Lambda function and add a Percentage: 10 property.

Question 8

A developer is using AWS CloudFormation to deploy a stack that includes an Amazon RDS DB instance. The developer wants to update the DB instance to a larger instance type without causing downtime. The current template has DeletionPolicy set to 'Delete'. What should the developer do?

Accepted Answer

Use a blue/green deployment by creating a new stack with the larger instance type and updating the application to point to the new database.. Option B is correct because a blue/green deployment allows you to create a new stack with the larger DB instance type in a separate environment (green), then switch the application traffic to the new database with minimal downtime. This approach avoids the downtime associated with in-place modifications, as CloudFormation updates to RDS instance types typically require a reboot, which causes an outage. By using a blue/green deployment, the developer can validate the new instance and cut over seamlessly.

Answer

Take a snapshot of the DB instance and restore it to a larger instance type.

Answer

Change the DeletionPolicy to 'Retain' and update the stack.

Answer

Create a read replica with the larger instance type and promote it.

Question 9

A developer is deploying a serverless application using the AWS Serverless Application Model (SAM). The application consists of an API Gateway, a Lambda function, and a DynamoDB table. The developer wants to enable canary deployments for the Lambda function. What should the developer do?

Accepted Answer

Add the AutoPublishAlias and DeploymentPreference properties to the Lambda function in the SAM template.. Option C is correct because the AWS SAM template supports canary deployments for Lambda functions by adding the `AutoPublishAlias` property (which automatically creates and publishes a new version to a Lambda alias) and the `DeploymentPreference` property (which defines the traffic-shifting strategy, such as `Canary10Percent5Minutes`). This enables CodeDeploy to gradually shift traffic from the current version to the new version without manual intervention.

Answer

Configure a CodeDeploy deployment group in the SAM template.

Answer

Create a Lambda alias and configure traffic shifting manually.

Answer

Use AWS CodePipeline to orchestrate the canary deployment.

Question 10

A developer is deploying a Python application to AWS Lambda. The application has several dependencies. The developer wants to ensure that the deployment package is as small as possible to reduce cold start times. What should the developer do?

Accepted Answer

Use Lambda Layers to manage dependencies separately from the function code.. Lambda Layers allow you to package and manage dependencies (like Python libraries) separately from your function code. By moving dependencies to a layer, the function code deployment package becomes smaller, which reduces the time Lambda spends downloading and extracting the package during cold starts. Layers are cached across executions, further improving performance.

Answer

Use an S3 bucket to store the deployment package.

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Use AWS CodeBuild to optimize the package.

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Include all dependencies in the deployment package.

Question 11

A developer is using Amazon DynamoDB for a new application. The developer wants to reduce read latency. Which design pattern should the developer use?

Accepted Answer

Use DynamoDB Accelerator (DAX) as a cache for frequently read items.. DynamoDB Accelerator (DAX) is an in-memory cache designed specifically for DynamoDB, providing microsecond read latency for frequently accessed items. By caching read-heavy workloads, DAX offloads requests from the DynamoDB table, reducing read latency without requiring application-level caching logic. This directly addresses the developer's goal of reducing read latency.

Answer

Create a global secondary index (GSI) for the table.

Answer

Increase the provisioned read capacity units (RCUs) for the table.

Answer

Use DynamoDB Global Tables to replicate data to multiple regions.

Question 12

A developer is troubleshooting an AWS Elastic Beanstalk environment that is failing health checks. The environment runs a web application on Tomcat. The developer checks the logs and finds no errors. What is the most likely cause of the health check failure?

Accepted Answer

The application's health check URL is returning a non-200 status code.. The most likely cause is that the application's health check URL is returning a non-200 status code. Elastic Beanstalk uses the load balancer to perform health checks against a configurable path (default: /). If the application responds with any status other than 200 OK, the load balancer marks the instance as unhealthy, even if the application logs show no errors. This is a common misconfiguration where the health check endpoint is not implemented or returns an unexpected status.

Answer

The security group for the instances does not allow traffic from the load balancer.

Answer

The application is throwing exceptions that are not logged.

Answer

The application is listening on a port other than 80.

Question 13

A company uses AWS CodePipeline to automate deployments. The pipeline has a source stage that pulls from Amazon S3, a build stage using AWS CodeBuild, and a deploy stage using AWS CloudFormation. The deploy stage often fails because CloudFormation change sets are not being created. What is the most likely cause?

Accepted Answer

The CloudFormation deploy action is configured to use the 'CREATE_AND_EXECUTE' change set mode, but the stack does not exist yet.. Option B is correct because when a CloudFormation deploy action in CodePipeline is configured with the 'CREATE_AND_EXECUTE' change set mode, it requires the stack to already exist. If the stack does not exist, CloudFormation cannot create a change set (since change sets compare changes against an existing stack), causing the deploy stage to fail. This is a common misconfiguration when deploying a new stack for the first time via CodePipeline.

Answer

The CodeBuild project is not producing the expected output artifacts.

Answer

The CloudFormation service role is missing.

Answer

The source stage is not configured to detect changes in the S3 bucket.

Question 14

A developer is using Amazon API Gateway with a Lambda integration. The API returns a 502 Bad Gateway error. The developer checks the Lambda function logs and finds no invocations. What is the most likely cause?

Accepted Answer

The API Gateway does not have permission to invoke the Lambda function.. A 502 Bad Gateway error from API Gateway with Lambda integration typically indicates that the Lambda function either returned an invalid response or was not invoked at all. Since the Lambda logs show no invocations, the most likely cause is that API Gateway lacks the necessary resource-based policy permission to invoke the Lambda function. Without this permission, API Gateway cannot trigger the function, resulting in a 502 error without any invocation record.

Answer

The Lambda function is returning a non-JSON response.

Answer

The Lambda function is timing out due to a long-running operation.

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The Lambda function's memory is insufficient, causing it to crash.

Question 15

A developer notices that an EC2 instance running a web application is unreachable via its public IP. The instance passes status checks but security group rules appear correct. What should the developer check NEXT?

Accepted Answer

Check the network ACL associated with the subnet for rules that may block traffic.. The instance passes status checks and security group rules appear correct, which rules out OS-level and security group issues. Since the instance is unreachable via its public IP, the next logical step is to check the network ACL (NACL) associated with the subnet, because NACLs are stateless and can block inbound or outbound traffic even if security groups allow it. NACLs evaluate rules in order by rule number, and a deny rule (or missing allow rule) for the required ephemeral ports (e.g., 1024-65535 for return traffic) could silently drop packets.

Answer

Verify that the instance has an Elastic IP associated.

Answer

Review the route table for a route to an internet gateway.

Answer

Inspect the IAM role attached to the instance for network permissions.

Question 16

A company uses AWS CodeDeploy to deploy a web application to an Auto Scaling group. The deployment fails with the error 'The overall deployment failed because too many individual instances failed deployment'. The deployment configuration is set to CodeDeployDefault.OneAtATime. What is the most likely cause of this failure?

Accepted Answer

The deployment failed on a single instance, causing the overall deployment to fail because the minimum number of healthy hosts was not maintained.. With CodeDeployDefault.OneAtATime, the deployment updates one instance at a time and requires that a minimum number of healthy hosts be maintained throughout the process. If a single instance fails its deployment, the overall deployment fails because the minimum healthy host threshold is breached—CodeDeploy cannot proceed to the next instance without risking service availability. This error indicates that the failure on one instance caused the entire deployment to abort, not that multiple instances failed independently.

Answer

The instances in the Auto Scaling group are not running a supported operating system.

Answer

The deployment configuration should be changed to AllAtOnce to avoid this error.

Answer

The IAM role for CodeDeploy does not have sufficient permissions.

Question 17

A developer is deploying a static website to Amazon S3 and wants to use Amazon CloudFront for content delivery. The developer wants to ensure that only CloudFront can access the S3 bucket. Which S3 bucket policy should the developer use?

Accepted Answer

Grant CloudFront access via an origin access identity (OAI) and restrict the bucket policy to the OAI.. Option D is correct because an Origin Access Identity (OAI) is a special CloudFront user that you can associate with your distribution. By configuring the S3 bucket policy to grant access only to that OAI, you ensure that direct S3 requests are denied, and only requests routed through CloudFront can retrieve objects. This provides a secure, private origin without exposing the bucket publicly.

Answer

Use a bucket policy that allows access only if the Referer header matches the CloudFront distribution domain.

Answer

Make the bucket public and use CloudFront's default caching.

Answer

Grant CloudFront access by allowing the CloudFront IP address range.

Question 18

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.. Option A is correct because `.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.

Answer

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

Answer

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

Question 19

A company is using AWS CodeDeploy with an in-place deployment to an Auto Scaling group. The deployment fails with the error 'Deployment failed because the deployment group does not have enough instances to deploy to'. The Auto Scaling group has a minimum size of 2, maximum size of 5, and desired capacity of 2. The deployment configuration is CodeDeployDefault.AllAtOnce. What is the most likely cause?

Accepted Answer

The deployment group has only 2 instances, and the deployment failed on one instance, causing the minimum healthy hosts threshold to be violated.. The error 'Deployment failed because the deployment group does not have enough instances to deploy to' occurs when the number of healthy instances in the deployment group falls below the minimum required by the deployment configuration. With CodeDeployDefault.AllAtOnce, the minimum healthy hosts threshold is 0, but the deployment still requires at least one healthy instance to succeed. In this scenario, the Auto Scaling group has a desired capacity of 2, and if one instance fails during deployment, the remaining healthy instance count drops to 1, which violates the implicit requirement that the deployment must complete on all instances without exceeding the failure threshold. The error message is misleading but points to the fact that the deployment failed on one instance, leaving the group with insufficient healthy hosts to meet the deployment's success criteria.

Answer

The Auto Scaling group needs to have at least 3 instances to use AllAtOnce.

Answer

The deployment configuration is not compatible with Auto Scaling groups.

Answer

The instances in the Auto Scaling group are not passing health checks.

Question 20

A company is deploying a new microservice using AWS CodeDeploy. The deployment group uses an EC2/On-Premises compute platform with an in-place deployment configuration. After the deployment, the new application version is not receiving traffic. The previous version continues to serve requests. What is the most likely cause?

Accepted Answer

The deployment group is not associated with a load balancer or target group.. In an in-place deployment with CodeDeploy on the EC2/On-Premises compute platform, traffic is routed to the new application version by a load balancer. If the deployment group is not associated with a load balancer or target group, CodeDeploy cannot register the instances or shift traffic to the new version, so the previous version continues serving requests. The deployment itself may succeed, but without the load balancer integration, the new application revision never receives incoming traffic.

Answer

The application revision is not stored in the correct S3 bucket.

Answer

The deployment configuration is set to CodeDeployDefault.OneAtATime.

Answer

The CodeDeploy agent is not installed on the EC2 instances.