DVA-C02 Practice Test 42 — 15 Questions

Question 1

A company uses Amazon API Gateway to expose a REST API backed by AWS Lambda. The API is experiencing high latency. The developer suspects cold starts are contributing to the latency. Which action would be MOST effective in reducing cold start latency?

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

Accepted Answer

Increase the memory allocation of the Lambda function.. Increasing the memory allocation of a Lambda function directly correlates to allocating more CPU power, which reduces the initialization time during a cold start. AWS Lambda provisions CPU proportionally to the configured memory, so a higher memory setting speeds up the runtime environment setup and code loading, thereby lowering cold start latency.

Answer

Place the Lambda function in a VPC to improve network latency.

Answer

Enable Lambda@Edge to cache responses.

Answer

Increase the function timeout to 15 minutes.

Question 2

A company uses AWS Elastic Beanstalk to deploy a Python web application. After a successful deployment, the environment's health turns 'Severe' and the application returns HTTP 502 errors. What is the most likely cause?

Accepted Answer

The application's requirements.txt file is missing a required dependency.. A missing dependency in requirements.txt causes the Python application to fail during startup, leading to the EC2 instances reporting an unhealthy status to the Elastic Load Balancer. Elastic Beanstalk relies on the application process to respond to health checks; if the app crashes due to an ImportError, the load balancer receives no valid HTTP response and returns 502 Bad Gateway errors. The environment health turns 'Severe' because the platform detects that the application process is not running or is failing repeatedly.

Answer

The EC2 instances have insufficient storage for the deployment.

Answer

The load balancer's health check path is incorrectly configured.

Answer

The RDS database connection string is incorrect.

Question 3

A company is using AWS CodePipeline to automate deployments. The pipeline has a source stage that retrieves code from Amazon S3, a build stage using AWS CodeBuild, and a deploy stage using AWS CodeDeploy. The build stage is failing intermittently with errors related to missing dependencies. What should a developer do to ensure the build environment has all required dependencies?

Accepted Answer

Create a custom buildspec.yml file in the source code that installs the dependencies in the install phase.. The buildspec.yml file defines the build phases for AWS CodeBuild, including the install phase where you can specify commands to install dependencies (e.g., using package managers like pip, npm, or apt-get). By placing this file in the source code, the build environment automatically executes these commands on every build, ensuring all required dependencies are present and consistent across runs, which resolves intermittent failures caused by missing dependencies.

Answer

Configure environment variables in CodePipeline to set dependency paths.

Answer

Manually install dependencies on the CodeBuild build server each time.

Answer

Use AWS CodeCommit as the source repository instead of S3.

Question 4

A company runs a web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application stores session state in an S3 bucket. Users report that after logging in, they are sometimes redirected to the login page again on subsequent requests. What is the MOST likely cause?

Accepted Answer

S3 is not a suitable store for session state due to its higher latency compared to in-memory stores like ElastiCache or DynamoDB.. Amazon S3 now provides strong read-after-write consistency, so eventual consistency is not the cause. However, S3's higher latency compared to in-memory stores like ElastiCache or DynamoDB makes it unsuitable for session management, which requires fast, frequent reads and writes. The higher latency can cause delays in session retrieval, leading to timeouts and the login page being displayed again.

Answer

The EC2 instances do not have internet access to reach S3.

Answer

The ALB does not have sticky sessions enabled.

Answer

The application is not scaling properly, causing session loss.

Question 5

A developer has set up an AWS CodePipeline pipeline that automatically deploys a web application through a series of stages: Source, Build, Staging, and Production. The developer wants to require a manual approval before the pipeline proceeds to the Production stage. How should the developer implement this?

Accepted Answer

Add a manual approval action between the Staging and Production stages. AWS CodePipeline supports manual approval actions that can be added as a stage or between stages to pause the pipeline and require explicit approval before proceeding. By placing the manual approval action between the Staging and Production stages, the pipeline will halt after the Staging stage completes and wait for an approver to manually approve the transition to the Production stage, ensuring no automatic deployment to production occurs without human oversight.

Answer

Add a manual approval action in the Staging stage

Answer

Configure the Production stage to use a CloudFormation change set with execution role

Answer

Use an SNS topic to notify developers of the deployment

Question 6

A developer has an AWS Lambda function that processes messages from an Amazon SQS standard queue. The function is idempotent and currently has a batch size of 10. The developer wants to increase throughput and increases the batch size to 100. After the change, CloudWatch metrics show a significant increase in throttles and the queue backlog is growing. The function's reserved concurrency is set to 10. What is the most effective action to resolve the throttling and improve throughput?

Accepted Answer

Increase the reserved concurrency of the Lambda function. Increasing the reserved concurrency from 10 to a higher value directly addresses the root cause of throttling. With a batch size of 100, each invocation processes more messages, but the function's reserved concurrency of 10 limits the maximum number of concurrent executions to 10. This means the Lambda service can only invoke the function 10 times at once, regardless of how many messages are in the queue. By raising reserved concurrency, you allow more concurrent invocations to handle the larger batches, reducing throttling and improving throughput.

Answer

Increase the memory allocation of the Lambda function

Answer

Switch the SQS queue to a FIFO queue

Answer

Decrease the batch size back to 10

Question 7

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 8

A developer wants to deploy a containerized application on AWS. The application requires persistent storage that can be accessed by multiple containers running on different EC2 instances. Which AWS service should the developer use?

Accepted Answer

Amazon Elastic File System (EFS). Amazon EFS provides a fully managed, scalable, and elastic NFS file system that can be mounted concurrently on multiple EC2 instances across different Availability Zones. This makes it the ideal choice for a containerized application requiring shared persistent storage accessible by multiple containers running on different instances, as it supports the NFSv4.1 and NFSv4.0 protocols for simultaneous access.

Answer

Amazon Elastic Block Store (EBS)

Answer

Amazon Simple Storage Service (S3)

Answer

Amazon DynamoDB

Question 9

A developer is using AWS CodeDeploy to perform a canary deployment for an AWS Lambda function. The deployment should first shift 10% of traffic to the new version, and then shift the remaining 90% after 5 minutes. Which deployment configuration should be used?

Accepted Answer

Canary10Percent5Minutes. The Canary10Percent5Minutes deployment configuration is specifically designed for canary deployments with AWS Lambda, shifting 10% of traffic to the new version immediately and then automatically shifting the remaining 90% after a 5-minute interval. This matches the requirement exactly, as CodeDeploy uses this predefined configuration to orchestrate the traffic shift in two steps with a built-in wait period.

Answer

AllAtOnce

Answer

Linear10PercentEvery10Minutes

Answer

BlueGreen

Question 10

A developer wants to deploy a static website to AWS. The website content is stored in an S3 bucket. Which combination of actions is required to host the website? (Choose TWO.)

Accepted Answer

Enable static website hosting on the S3 bucket.. To host a static website on S3, you must enable static website hosting on the bucket (option B) and make the objects publicly readable (option E). Option A (server access logging) is optional for tracking requests, not required. Option C (restricting access to a specific IP) would prevent public access, which is needed for a public website. Option D (CloudFront) is an optional CDN service, not a requirement for S3 static website hosting.

Answer

Enable server access logging.

Answer

Set a bucket policy that restricts access to a specific IP.

Answer

Configure Amazon CloudFront as a CDN.

Question 11

A company is using AWS CodeDeploy to deploy an application to an Auto Scaling group. The deployment fails with 'The overall deployment failed because too many individual instances failed deployment, too few healthy instances are available for deployment, or some instances in your deployment group are experiencing problems.' The developer wants to identify the specific error on a failed instance. Which AWS CLI command should the developer use?

Accepted Answer

aws deploy get-deployment-instance. The `aws deploy get-deployment-instance` command retrieves detailed information about a single instance in a deployment group, including the specific error messages and lifecycle event logs that caused the instance to fail. This allows the developer to diagnose the root cause of the failure on a particular instance, which is exactly what is needed when the overall deployment fails with a generic error message.

Answer

aws deploy get-deployment

Answer

aws deploy list-deployments

Answer

aws deploy list-deployment-instances

Question 12

A developer is using AWS CodeDeploy to deploy an application to an EC2 Auto Scaling group. The deployment must ensure that a minimum number of instances are always running and healthy. The developer wants to deploy to 10 instances. Which deployment configuration should the developer use?

Accepted Answer

CodeDeployDefault.OneAtATime. CodeDeployDefault.OneAtATime, is correct because it ensures that only one instance is updated at a time, which guarantees that a minimum number of instances (9 out of 10) remain healthy and running throughout the deployment. This configuration is ideal for maintaining high availability and meeting strict uptime requirements.

Answer

CodeDeployDefault.AllAtOnce

Answer

CodeDeployDefault.HalfAtATime

Answer

CodeDeployDefault.MinHealthyHostsPercentage: 90

Question 13

A company has a Node.js application running on an EC2 instance. The application needs to store session state. The developer wants to ensure high availability and scalability by storing session data externally. Which AWS service is BEST suited for this purpose?

Accepted Answer

Amazon ElastiCache for Redis. Amazon ElastiCache for Redis is the best choice for external session storage because it provides an in-memory data store with sub-millisecond latency, which is critical for session state access in a high-traffic Node.js application. Redis supports data structures like hashes and TTL (time-to-live) for automatic session expiration, and it can be clustered for high availability and scalability, making it ideal for stateless EC2 instances behind a load balancer.

Answer

Amazon DynamoDB

Answer

Amazon S3

Answer

Amazon RDS for MySQL

Question 14

A developer is using IAM roles to grant permissions to an EC2 instance. Which TWO statements are true about IAM roles for EC2?

Accepted Answer

Temporary security credentials are obtained from the instance metadata service.. An EC2 instance obtains temporary security credentials from the instance metadata service (http://169.254.169.254/latest/meta-data/iam/security-credentials/). Option E is correct because you can attach an IAM role to a running EC2 instance using the AWS CLI or console without stopping the instance. Option A is incorrect because an EC2 instance can have only one IAM role attached at a time (via an instance profile). Option C is incorrect because temporary credentials are automatically refreshed by the AWS SDKs and CLI before they expire (default expiry is 6 hours, but refresh is automatic). Option D is incorrect because the same IAM role can be attached to multiple EC2 instances simultaneously (via the same instance profile).

Answer

An EC2 instance can have multiple IAM roles attached simultaneously.

Answer

The temporary credentials expire after 6 hours and must be manually refreshed.

Answer

An IAM role can only be attached to one EC2 instance at a time.

Question 15

A company runs a stateful web application on EC2 instances in an Auto Scaling group. Users report that their session data is lost when instances are replaced during scaling events. What is the best solution to preserve session state?

Accepted Answer

Use ElastiCache as a centralized session store.. ElastiCache provides a centralized, in-memory session store that is external to the EC2 instances. This ensures session data persists independently of the instance lifecycle, so when an instance is replaced during a scaling event, the new instance can retrieve the session from ElastiCache, preserving user state. This is the best solution because it decouples session state from compute resources, aligning with the stateless application pattern recommended for Auto Scaling groups.

Answer

Enable sticky sessions on the Application Load Balancer.

Answer

Store sessions in the Application Load Balancer.

Answer

Use an S3 bucket to store session data.