DVA-C02 Practice Test 47 — 15 Questions

Question 1

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?

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

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 2

A developer is deploying a new version of an AWS Lambda function using the AWS CLI. The function is currently active and handling traffic. The developer wants to gradually shift traffic to the new version and rollback if errors increase. Which TWO actions should the developer take? (Choose TWO.)

Accepted Answer

Configure the alias to route a percentage of traffic to the new version and the rest to the current version.. Lambda aliases support weighted routing, allowing you to specify a percentage of traffic to send to a new version while the remainder goes to the current version. This enables canary deployments where you can monitor error rates and rollback by adjusting the weights without redeploying.

Answer

Invoke the Lambda function with the new version using the AWS SDK.

Answer

Update the alias to route 100% of traffic to the new version.

Answer

Use AWS CodeDeploy to create a deployment group for the Lambda function.

Question 3

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.

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The application is listening on a port other than 80.

Question 4

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)

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Amazon Simple Storage Service (S3)

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Amazon DynamoDB

Question 5

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 6

A company runs a web application on EC2 instances behind an Application Load Balancer (ALB). The application stores session data in an RDS MySQL database. Recently, users have reported that they are being logged out unexpectedly and their session data is lost. The developer investigates and finds that the RDS instance's CPU utilization spikes periodically, coinciding with the logout events. The application uses connection pooling via an RDS Proxy. The developer suspects that the session table is being dropped or truncated. After checking the application logs, the developer finds no evidence of truncation commands. The RDS instance has automated backups enabled, and the binary logs are retained for 24 hours. The developer wants to identify the root cause and prevent future occurrences. Which course of action should the developer take?

Accepted Answer

Check the session table's storage engine; if it uses MEMORY, change it to InnoDB to persist data across restarts.. The MEMORY storage engine in MySQL stores table data in RAM and loses all rows when the MySQL server restarts (e.g., during a crash, failover, or maintenance). The periodic CPU spikes and session loss without any TRUNCATE/DROP in the logs strongly indicate the session table is using MEMORY and being wiped on restart. Converting the table to InnoDB persists data to disk and survives restarts, resolving the issue.

Answer

Enable Multi-AZ deployment for RDS to improve availability and prevent data loss during failover.

Answer

Increase the RDS instance size to handle the CPU spikes and prevent future issues.

Answer

Disable RDS Proxy and implement connection pooling in the application code to reduce database load.

Question 7

A developer is configuring a load balancer in front of an EC2 instance running a web application. The application needs to authenticate users via an identity provider. Which AWS service should the developer use to handle authentication and authorization?

Accepted Answer

Amazon Cognito. Amazon Cognito is designed to handle user authentication and authorization for web and mobile applications. It provides user pools for sign-up/sign-in and identity pools for federated identities, allowing integration with external identity providers (IdPs) like Google, Facebook, and SAML. Since the application needs to authenticate users via an identity provider, Cognito is the correct choice.

Answer

AWS Identity and Access Management (IAM)

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Amazon Route 53

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Amazon CloudFront

Question 8

A developer needs to securely store database credentials for a serverless application. Which service should be used?

Accepted Answer

AWS Secrets Manager. AWS Secrets Manager is purpose-built for storing, rotating, and retrieving secrets such as database credentials, with native integration to RDS rotation Lambdas and fine-grained IAM access. It encrypts secrets with KMS and supports automatic rotation, which is the key differentiator for credential storage.

Answer

AWS Systems Manager Parameter Store

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Amazon S3

Answer

AWS Key Management Service (KMS)

Question 9

An organization uses AWS CodeCommit for source control and AWS CodeBuild for building a Java application. The build process needs to run integration tests that require a MySQL database. The team wants to ensure the database is provisioned only during the build and cleaned up afterward to minimize costs. What is the most efficient solution?

Accepted Answer

Use a Docker container running MySQL within the CodeBuild environment.. Running MySQL inside a Docker container within the CodeBuild environment is the most efficient solution because the database is ephemeral, starts and stops with the build, and incurs no persistent infrastructure cost. CodeBuild supports Docker via the privileged mode setting, and the container can be started in the buildspec's pre_build phase and torn down automatically when the build finishes. This satisfies the requirement to provision only during the build and clean up afterward.

Answer

Provision a small RDS MySQL instance and keep it running for the build process.

Answer

Use AWS CloudFormation to create an RDS instance at the start of the build and delete it at the end.

Answer

Use Amazon DynamoDB as a substitute for MySQL for the integration tests.

Question 10

A developer is troubleshooting an AWS Lambda function that processes messages from an Amazon SQS queue. The function is configured with a batch size of 10 and a maximum concurrency of 5. The function frequently reports errors related to message processing timeouts. The function code is idempotent. Which combination of actions will reduce the number of timeouts and improve processing efficiency?

Accepted Answer

Reduce the batch size to 5 and increase the maximum concurrency to 10.. Reducing the batch size to 5 decreases the number of messages processed per invocation, lowering the processing time and reducing the likelihood of timeouts. Increasing maximum concurrency to 10 allows more Lambda functions to run in parallel, improving overall throughput. Option A is wrong: increasing the Lambda timeout to 30 seconds alone does not address the root cause (overloaded invocations), and setting the SQS visibility timeout to 6 minutes may cause delayed retries if messages fail. Option B is wrong: increasing the batch size to 20 would increase the processing time per invocation, exacerbating timeouts. Option D is wrong: increasing concurrency to 10 helps parallelism but does not reduce the per-invocation workload; setting visibility timeout to 30 seconds is too short, risking message duplication if processing exceeds that time.

Answer

Increase the function timeout to 30 seconds and set the SQS visibility timeout to 6 minutes.

Answer

Increase the batch size to 20 and increase the function timeout to 30 seconds.

Answer

Increase the maximum concurrency to 10 and set the SQS visibility timeout to 30 seconds.

Question 11

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 12

The exhibit shows a CloudFormation template that creates an S3 bucket with versioning enabled. After deploying the stack, a developer uploads an object to the bucket. Later, the developer updates the object by uploading a new version. The developer wants to retrieve the original object. What is the correct way to do this?

Accepted Answer

Use the S3 console or CLI to list object versions and retrieve the version ID of the original object.. With S3 versioning enabled, uploading a new version of an object does not overwrite the original — it creates a new version and retains the previous one. The developer can retrieve the original by listing object versions (via console or aws s3api list-object-versions) to find the original version ID, then downloading that specific version.

Answer

Restore the original object using the S3 Object Lambda.

Answer

Use the S3 Batch Operations to revert to the original version.

Answer

The original object is overwritten and cannot be retrieved.

Question 13

A company uses AWS CodeDeploy to deploy an application to EC2 instances. The deployment fails with the error: 'The overall deployment failed because too many individual instances failed deployment, too few healthy instances are available, or some instances in your deployment group are experiencing problems.' The deployment group consists of 4 EC2 instances. The deployment configuration is 'CodeDeployDefault.OneAtATime'. The CodeDeploy agent logs on the failed instance show: 'Error: Script at specified location: scripts/install_dependencies.sh failed with exit code 1.' What should the developer do to resolve this issue?

Accepted Answer

Review the install_dependencies.sh script for errors and correct them.. The error message clearly indicates that the install_dependencies.sh script failed with exit code 1 on the instance. The root cause is a problem within the script itself (e.g., a failed package install, missing dependency, or syntax error). The developer must review and correct the script to resolve the deployment failure.

Answer

Change the deployment configuration to 'CodeDeployDefault.AllAtOnce'.

Answer

Reinstall the CodeDeploy agent on the failed instance.

Answer

Increase the number of EC2 instances in the deployment group.

Question 14

A company runs a web application on EC2 instances in an Auto Scaling group. The application needs to store session state. The architecture must be highly available and scalable. Which solution should the developer choose?

Accepted Answer

Use Amazon ElastiCache for Redis to store session state. Amazon ElastiCache for Redis is a fully managed, highly available, and scalable in-memory data store that is purpose-built for session state management. It supports replication, automatic failover, and horizontal scaling, making it the ideal choice for a highly available and scalable session store across an Auto Scaling group of EC2 instances.

Answer

Use sticky sessions on the Application Load Balancer

Answer

Store session data in an S3 bucket

Answer

Store session data in the instance's ephemeral storage

Question 15

A developer performed a CodeDeploy deployment to an Auto Scaling group. The deployment status is Failed with code HEALTH_CONSTRAINTS. Based on the exhibit, what is the most likely cause?

Accepted Answer

The minimum number of healthy instances required for the deployment was not met. The HEALTH_CONSTRAINTS error in CodeDeploy means the deployment could not maintain the minimum number of healthy instances specified in the deployment configuration during the deployment. This typically occurs when instances fail health checks, the ASG cannot launch replacements fast enough, or the deployment configuration's minimum healthy hosts threshold is too high relative to available capacity. The most likely cause is that the minimum healthy instance requirement was not met.

Answer

The CodeDeploy agent on the instances is not running

Answer

The application revision contains invalid scripts

Answer

The IAM role for CodeDeploy does not have sufficient permissions