DOP-C02 Practice Test 3 — 25 Questions

Question 1

A company stores sensitive data in Amazon S3. A security audit reveals that several S3 buckets are publicly accessible. The DevOps engineer needs to implement a solution that automatically detects and alerts on any S3 bucket that becomes public. Which AWS service should the engineer use?

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

Accepted Answer

Amazon Macie. Amazon Macie uses machine learning to discover, classify, and protect sensitive data, and it can automatically detect and alert on S3 buckets that become publicly accessible. Option B is incorrect because S3 Block Public Access is a preventive control, not detective. Option C is incorrect because AWS Trusted Advisor can check for public buckets but does not provide real-time alerts. Option D is incorrect because AWS Config can track bucket policies but does not automatically alert on public access.

Answer

S3 Block Public Access

Answer

AWS Trusted Advisor

Answer

AWS Config

Question 2

A company uses AWS CodePipeline to deploy a serverless application using AWS SAM. The pipeline has a source stage from CodeCommit, a build stage that runs 'sam build', and a deploy stage that runs 'sam deploy --no-confirm-changeset'. The deploy stage fails with the error 'The security token included in the request is invalid.' What is the MOST likely cause?

Accepted Answer

The IAM role used by CodeBuild has expired credentials or insufficient permissions to call AWS CloudFormation.. The error 'The security token included in the request is invalid' indicates that the AWS credentials used by CodeBuild to call the CloudFormation API are either expired or lack the necessary permissions. In a CodePipeline with a CodeBuild action, the build project assumes an IAM role to perform actions such as 'sam deploy', which internally calls CloudFormation. If that IAM role's temporary credentials have expired (e.g., due to a long-running build) or the role does not have the required CloudFormation permissions (e.g., cloudformation:CreateChangeSet, cloudformation:ExecuteChangeSet), the API call will fail with this exact error.

Answer

The CloudFormation stack is in a 'ROLLBACK_COMPLETE' state and cannot be updated.

Answer

The CodeBuild project does not have access to the CodeCommit repository.

Answer

The SAM template is invalid and contains syntax errors.

Question 3

A DevOps engineer is troubleshooting a slow web application. The application runs on EC2 instances behind an ALB. The engineer notices that the ALB's TargetResponseTime metric shows high p99 values, but the CPU and memory on the EC2 instances are well below thresholds. What is the most likely cause?

Accepted Answer

The application is waiting on a slow database query or external API call. High p99 TargetResponseTime on the ALB with low CPU and memory on the EC2 instances indicates that the bottleneck is not compute capacity but rather a dependency external to the application server. The application is likely waiting on a slow database query or external API call, which increases response time without consuming significant local CPU or memory. This is a classic symptom of an I/O-bound or network-bound dependency.

Answer

The Auto Scaling group has too many instances, causing increased network overhead

Answer

The ALB is routing requests to instances in different Availability Zones, increasing latency

Answer

The ALB idle timeout is set too low, causing connections to be dropped

Question 4

A company runs a serverless application using AWS Lambda functions that process messages from an Amazon SQS queue. The function scales up to handle high traffic but sometimes experiences throttling errors (HTTP 429) from Lambda. The company wants to improve the resilience of the application by reducing throttling. The SQS queue is configured as a Lambda event source with a batch size of 10. The Lambda function has a reserved concurrency of 100. Which combination of actions will best reduce throttling? (Choose the single best answer.)

Accepted Answer

Increase the Lambda function's reserved concurrency to 500.. Throttling errors (HTTP 429) occur when Lambda function invocations exceed the account-level concurrency limit or the function's reserved concurrency. By increasing the reserved concurrency from 100 to 500, the function can handle more concurrent invocations, reducing the likelihood of throttling when traffic spikes. This directly addresses the scaling bottleneck without changing the event source or message processing pattern.

Answer

Change the SQS queue to use a FIFO queue to guarantee exactly-once processing.

Answer

Increase the SQS batch size to 50 to process more messages per invocation.

Answer

Use a dead-letter queue (DLQ) for unprocessed messages and set up a CloudWatch alarm to trigger a second Lambda function to reprocess them.

Question 5

A company uses AWS CloudFormation to deploy infrastructure. The DevOps team wants to receive notifications when a stack creation fails due to a resource limit exceeded error. Which approach should be used?

Accepted Answer

Configure an SNS topic as a notification option in the CloudFormation stack, and subscribe an email endpoint.. CloudFormation natively supports sending stack events (including creation failures) to an SNS topic. By configuring an SNS topic as a notification option in the stack creation request, the DevOps team can subscribe an email endpoint to receive real-time notifications when a resource limit exceeded error occurs, without needing additional services or custom logic.

Answer

Create an Amazon EventBridge rule that matches CloudFormation resource limit exceeded events and sends to SQS.

Answer

Use AWS Config to detect when a stack is in a failed state.

Answer

Enable CloudTrail and create a CloudWatch alarm on the CreateStack API call.

Question 6

A company is running a batch processing job on Amazon EMR that writes results to an Amazon S3 bucket. The job runs daily and takes about 2 hours. The DevOps team wants to be alerted if the job fails or takes longer than 3 hours. Which solution is the MOST cost-effective and operationally efficient?

Accepted Answer

Use Amazon CloudWatch Events to trigger an AWS Lambda function when the EMR cluster changes to 'TERMINATED' state, then check the job duration and send an alert if it exceeded 3 hours.. It uses CloudWatch Events to detect the EMR cluster's 'TERMINATED' state, which triggers a Lambda function that can check the job duration against the 3-hour threshold and send an alert via SNS if needed. This approach is cost-effective (no polling, event-driven) and operationally efficient, as it decouples monitoring from the job itself and handles both failure and timeout scenarios without modifying the EMR job code.

Answer

Configure Amazon Simple Notification Service (SNS) directly from the EMR job to send notifications on completion.

Answer

Create a CloudWatch alarm on the EMR cluster's EC2 instance CPUUtilization metric to detect abnormal runtime.

Answer

Use Amazon CloudWatch Logs to monitor the job's log stream and create a metric filter for 'FAILED' messages.

Question 7

Which TWO approaches can be used to manage configuration files (e.g., application.properties) across multiple AWS accounts and regions using AWS Systems Manager? (Select TWO.)

Accepted Answer

Use AWS AppConfig to create, manage, and deploy application configurations across accounts and regions.. AWS AppConfig is a feature of AWS Systems Manager that allows you to create, manage, and deploy application configurations across accounts and regions. It supports staged rollouts, validation, and monitoring, making it suitable for managing configuration files like application.properties in multi-account, multi-region environments.

Answer

Use AWS OpsWorks for Chef Automate to store configuration data in Chef data bags.

Answer

Store configuration files in AWS Secrets Manager and retrieve them using the Secrets Manager API.

Answer

Use AWS Systems Manager Run Command to push configuration files to EC2 instances on demand.

Question 8

A company has a multi-account strategy using AWS Organizations. The security team needs to respond to incidents across all accounts. They want to ensure that all CloudTrail trails are enabled and logging to a central S3 bucket in the management account. What is the MOST efficient way to monitor compliance?

Accepted Answer

Use AWS Config conformance packs with a managed rule to check CloudTrail is enabled.. AWS Config conformance packs with managed rules can be deployed across multiple accounts using StackSets or directly via AWS Organizations to check that CloudTrail trails are enabled and logging to a central S3 bucket. This provides centralized, automated compliance monitoring without manual per-account setup. Option A is wrong because CloudTrail Insights detects unusual API activity, not configuration compliance. Option C is wrong because setting up CloudWatch Events rules in each account is less efficient and harder to maintain than Config conformance packs. Option D is wrong because Trusted Advisor checks are per-account and cannot be centrally enforced across an organization.

Answer

Create a CloudTrail organization trail and use CloudTrail Insights to detect configuration changes.

Answer

Set up CloudWatch Events rules in each account to detect trail disabling.

Answer

Use AWS Trusted Advisor to check CloudTrail configuration in each account.

Question 9

A company is using AWS CloudTrail to log API calls. The security team needs to ensure that log files are tamper-proof and can be used to verify integrity. Which feature should be enabled?

Accepted Answer

CloudTrail log file integrity validation. CloudTrail log file integrity validation uses SHA-256 hashing and digital signing to ensure logs have not been tampered with. S3 object lock prevents deletion but not modification. MFA delete protects deletion but not modification. SSE encrypts data at rest but does not protect integrity.

Answer

Server-side encryption (SSE-S3)

Answer

S3 Object Lock

Answer

MFA delete on the S3 bucket

Question 10

A CloudFormation template snippet is shown. An engineer attempts to create a stack with this template and receives an error: 'Bucket my-unique-bucket-name already exists'. What is the most likely cause?

Accepted Answer

The S3 bucket name 'my-unique-bucket-name' is already taken by another AWS account.. S3 bucket names must be globally unique across all AWS accounts and regions. The error 'Bucket my-unique-bucket-name already exists' indicates that the name is already taken by another AWS account, not that the bucket already exists in the current account. CloudFormation cannot create the bucket because the name is not available in the global S3 namespace.

Answer

The bucket policy has a syntax error that prevents the bucket from being created.

Answer

The versioning configuration is incompatible with the bucket policy.

Answer

The bucket policy references the bucket name incorrectly, causing a circular dependency.

Question 11

A DevOps engineer is configuring AWS CloudTrail to log all management events across all regions. The engineer wants to ensure that log files are encrypted at rest using a customer-managed KMS key. What is the correct way to achieve this?

Accepted Answer

Specify a KMS key ID in the CloudTrail trail configuration and grant CloudTrail permissions to use the key.. AWS CloudTrail supports encryption at rest using a customer-managed AWS KMS key (SSE-KMS). To achieve this, you must specify the KMS key ID in the CloudTrail trail configuration and grant CloudTrail permissions to use that key via the key policy. Option A is wrong because CloudTrail does not support SSE-C (customer-provided keys); it only supports SSE-S3 or SSE-KMS. Option B is wrong because client-side encryption is not a built-in CloudTrail feature and would require custom implementation. Option C is wrong because SSE-S3 uses S3-managed keys, not a customer-managed KMS key. Therefore, D is the only correct way to encrypt CloudTrail logs with a customer-managed KMS key.

Answer

Use SSE-C with a customer-provided key when uploading logs to S3.

Answer

Enable client-side encryption before delivering logs to S3.

Answer

Enable default encryption on the S3 bucket using SSE-S3.

Question 12

A company uses AWS CodePipeline to deploy a Node.js application to AWS Elastic Beanstalk. The pipeline includes a build stage using AWS CodeBuild. Developers notice that the deployed application occasionally crashes due to missing environment variables that were configured in the Elastic Beanstalk environment but not passed from CodeBuild. What is the MOST efficient way to ensure the environment variables are consistently applied?

Accepted Answer

Define environment variables in the source code using .ebextensions configuration files.. Ebextensions configuration files allow you to define environment variables declaratively in the source code, ensuring they are consistently applied during every deployment via CodePipeline. This approach eliminates the dependency on runtime or manual steps, as the Elastic Beanstalk environment automatically reads these files during environment creation and updates. It integrates seamlessly with CodeBuild and CodePipeline, making it the most efficient and reliable method for maintaining environment variable consistency.

Answer

Update the environment variables manually in the Elastic Beanstalk console after each deployment.

Answer

Use the aws elasticbeanstalk update-environment CLI command after the pipeline completes.

Answer

Store environment variables in AWS Systems Manager Parameter Store and have the application retrieve them at runtime.

Question 13

A company uses Amazon RDS for MySQL with Multi-AZ deployment. The application experiences increased latency during peak hours. The DevOps engineer investigates and notices that the Read Replicas are not being utilized effectively. The application is configured to use the primary database endpoint. The engineer wants to offload read traffic to the Read Replicas without changing the application code. What is the BEST solution?

Accepted Answer

Configure Amazon RDS Proxy in front of the database and enable read/write splitting.. Amazon RDS Proxy with read/write splitting allows the application to offload read traffic to Read Replicas without code changes. It automatically directs read queries to Read Replicas and write queries to the primary, using a single endpoint. Option A (increasing instance size) does not leverage Read Replicas. Option B (modifying application) requires code changes. Option C (Multi-AZ cluster with read-only endpoint) is invalid because Multi-AZ clusters use a writer and reader endpoint, but the question requires no code changes, and the existing configuration uses a primary endpoint; also, creating a new cluster may not be the simplest solution compared to RDS Proxy.

Answer

Increase the instance size of the primary database to handle the load.

Answer

Modify the application to use separate endpoints for read and write operations.

Answer

Create a new Multi-AZ cluster with a read-only endpoint.

Question 14

Which TWO are correct about using AWS CloudFormation to manage infrastructure across multiple AWS accounts? (Select TWO.)

Accepted Answer

You can use AWS Organizations to centrally manage accounts and use StackSets with trusted access.. AWS Organizations can centrally manage accounts, and StackSets can be enabled with trusted access to deploy stacks across accounts. Option D is correct because AWS CloudFormation StackSets allow deploying stacks across multiple accounts. Option B is incorrect because CloudFormation cannot automatically create new AWS accounts. Option C is incorrect because nested stacks operate within a single stack and cannot deploy resources across different accounts from a single template. Option E is incorrect because cross-stack references only work within the same account and region.

Answer

CloudFormation can automatically create new AWS accounts using a template.

Answer

Nested stacks can be used to deploy resources in different accounts from a single template.

Answer

You can use cross-stack references to share resources between accounts.

Question 15

A company wants to use AWS OpsWorks for configuration management of their EC2 instances. They need to ensure that the instances are automatically configured with the latest security patches upon boot. Which OpsWorks feature should they use?

Accepted Answer

Create a custom Chef recipe that installs security patches and assign it to the setup lifecycle event.. AWS OpsWorks uses Chef recipes to manage instance configuration. By creating a custom Chef recipe that installs the latest security patches and assigning it to the 'setup' lifecycle event, the recipe runs automatically on every new instance boot, ensuring patches are applied before the instance enters service. This is the native OpsWorks mechanism for configuration management during instance provisioning.

Answer

Configure the instances to run a user data script that updates packages.

Answer

Use AWS Systems Manager Patch Manager with an OpsWorks lifecycle event.

Answer

Use a CloudFormation template to apply patches during stack creation.

Question 16

A team uses AWS CodePipeline to deploy a serverless application using AWS SAM. The pipeline includes a build stage that runs 'sam build' and a deploy stage that runs 'sam deploy'. The deployment fails with an error: 'The security token included in the request is invalid.' What is the MOST likely cause?

Accepted Answer

The IAM role used in the deploy stage does not have permission to assume the CloudFormation execution role.. The error 'The security token included in the request is invalid' typically occurs when the IAM role used by CodePipeline in the deploy stage lacks the necessary trust relationship or permissions to assume the CloudFormation execution role. In AWS SAM deployments via CodePipeline, the deploy action uses a specified IAM role to call CloudFormation, and if that role cannot assume the CloudFormation service role (or the CloudFormation role itself is misconfigured), the security token becomes invalid. This is a common misconfiguration when the pipeline's IAM role does not include the 'sts:AssumeRole' permission for the CloudFormation execution role ARN.

Answer

The build stage did not produce the correct output artifact.

Answer

The SAM template has a syntax error.

Answer

The 'sam deploy' command is missing the '--capabilities' parameter.

Question 17

A company uses AWS CodeDeploy to deploy an application to an Auto Scaling group. The deployment fails with the error '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 deployment is set to 'AllAtOnce'. The application revision is a simple index.html. What is the most likely cause?

Accepted Answer

The CodeDeploy agent is not installed or running on the EC2 instances.. The error message indicates that too many instances failed deployment, which is typical when the CodeDeploy agent is not running on the EC2 instances. With an 'AllAtOnce' deployment, all instances are targeted simultaneously, so if the agent is missing on every instance, all will fail immediately, causing the overall deployment to fail. The simple index.html revision is not the issue; the agent is required to execute the AppSpec file and pull the revision from S3 or GitHub.

Answer

The IAM instance profile does not have permissions to download from Amazon S3.

Answer

The application revision is not a compressed archive.

Answer

The deployment configuration 'AllAtOnce' is incompatible with Auto Scaling groups.

Question 18

A company uses AWS CodeBuild to compile a Java application. The buildspec.yml includes a pre_build phase that runs unit tests and a build phase that packages the application. Recently, builds have been failing intermittently with 'OutOfMemoryError' during the test phase. The build environment is set to 'BUILD_GENERAL1_SMALL'. What is the MOST cost-effective solution?

Accepted Answer

Change the build environment to 'BUILD_GENERAL1_MEDIUM' which has more memory.. The 'BUILD_GENERAL1_SMALL' environment provides only 3 GB of memory, which is insufficient for the unit tests, causing intermittent 'OutOfMemoryError'. Upgrading to 'BUILD_GENERAL1_MEDIUM' (7 GB) directly addresses the memory shortage without architectural changes, and it is the most cost-effective solution because it avoids the complexity and additional costs of parallel jobs or test splitting while still resolving the root cause.

Answer

Split the tests into smaller batches using CodeBuild test splitting.

Answer

Configure the buildspec to set MAVEN_OPTS='-Xmx512m' to reduce JVM heap usage.

Answer

Use multiple CodeBuild jobs to run tests in parallel.

Question 19

A company is using a centralized logging solution with Amazon OpenSearch Service. The DevOps team notices that logs from some EC2 instances are missing. The CloudWatch agent is installed and configured on all instances. What should the team do to troubleshoot the issue?

Accepted Answer

Check the CloudWatch agent log file located at /var/log/amazon/amazon-cloudwatch-agent/amazon-cloudwatch-agent.log.. The CloudWatch agent writes detailed operational logs to /var/log/amazon/amazon-cloudwatch-agent/amazon-cloudwatch-agent.log. This file contains errors, warnings, and debug messages that can reveal why logs from specific EC2 instances are not being delivered to Amazon OpenSearch Service. Checking this log is the first and most direct troubleshooting step because it captures agent-level issues such as configuration errors, network connectivity failures, or permission problems.

Answer

Check the CloudWatch agent status using the CloudWatch agent status command.

Answer

Configure a Lambda function to poll the CloudWatch agent for logs.

Answer

Verify that the EC2 instances have an SQS queue configured for log delivery.

Question 20

A company runs a containerized application on Amazon ECS with Fargate launch type. The application is behind an Application Load Balancer (ALB). The operations team notices that the ALB's 5xx error rate increases periodically. The ECS service is configured with a target tracking scaling policy based on CPU utilization. The CloudWatch logs from the application show no errors. The health check on the ALB is configured to hit the /health endpoint. What is the MOST likely cause of the 5xx errors?

Accepted Answer

The health check endpoint is returning a 503 status due to a dependency failure.. The ALB periodically reports 5xx errors because the health check endpoint /health is returning a 503 status code, likely due to a transient dependency failure. When the health check fails, the ALB considers the target unhealthy and returns a 503 (or 502) to clients. The application code itself logs no errors because the failure occurs in a downstream dependency that the health check probes, not in the main application logic. Option A is incorrect because ECS with Fargate does not expose underlying host patching; the ALB would not detect such patching as 5xx errors. Option C is incorrect because a target tracking CPU scaling policy, even if slow, would not cause 5xx errors—it would affect performance but not directly trigger health check failures. Option D is incorrect because the application logs show no errors, ruling out unlogged exceptions as the source.

Answer

The ECS tasks are running on an underlying host that is being patched.

Answer

The target tracking scaling policy is not responding quickly enough to traffic spikes.

Answer

The application is throwing exceptions that are not logged.