DOP-C02 Hard Questions — 25 Difficult Questions

Question 1

A company uses AWS CodePipeline with multiple stages: Source (Amazon S3), Build (AWS CodeBuild), and Deploy (AWS CodeDeploy). The build stage runs a series of tests, and if they pass, the pipeline proceeds to deploy. Recently, a developer committed a change that passed all tests but caused a production outage. The team wants to add an approval step before the deploy stage, but they also want to ensure that only changes from specific branches can be deployed. What is the MOST secure and maintainable way to enforce this?

Accepted Answer

Create a separate pipeline for each allowed branch, with the approval step only in the production pipeline.. Option C is correct because it enforces branch-based deployment at the pipeline level, ensuring that only changes from specific branches trigger the production pipeline with the approval step. This approach is secure and maintainable as it leverages AWS CodePipeline's native ability to trigger on branch events, avoiding custom logic or manual verification. By isolating production deployments to a dedicated pipeline, the team reduces the risk of unauthorized or untested code reaching production.

Answer

Use a Lambda function in the pipeline to check the branch name and fail if not allowed.

Answer

Add a manual approval step in the pipeline and rely on the approver to verify the branch.

Answer

Tag the source artifacts with the branch name and use a condition in CodePipeline to allow only specific tags.

Question 2

An organization uses AWS CodePipeline to orchestrate deployments to multiple environments (dev, test, prod). Each environment uses a different AWS account. The pipeline uses cross-account actions with IAM roles. Recently, the pipeline failed at the deploy stage for the prod account with the error 'Access Denied' when assuming the cross-account role. The role ARN is correct and the trust policy allows the pipeline's service role. What is the MOST likely cause?

Accepted Answer

The pipeline's service role lacks the `sts:AssumeRole` permission for the cross-account role.. The pipeline's service role must have an `sts:AssumeRole` permission on the cross-account role to perform the role assumption. Even if the trust policy on the cross-account role allows the pipeline's service role, the pipeline's service role itself needs an IAM policy granting `sts:AssumeRole` for the cross-account role ARN. Without this permission, the `AssumeRole` API call fails with 'Access Denied', which is the exact error described.

Answer

The EC2 instances in the prod account do not have an appropriate instance profile.

Answer

The cross-account role's permissions boundary denies the deploy action.

Answer

The pipeline's service role does not have permission to perform the deploy action in the prod account.

Question 3

A DevOps team is designing a CI/CD pipeline for a microservices application. Each microservice has its own code repository and build artifacts. The team wants to use AWS CodePipeline with multiple parallel actions to build and test all microservices simultaneously. They also want to ensure that if one microservice's build fails, the pipeline does not block other microservices. Which THREE steps should the team take? (Choose THREE.)

Accepted Answer

Use a parallel action group with separate build actions for each microservice.. Option A is correct because using a parallel action group with separate build actions for each microservice allows all microservices to be built simultaneously within a single pipeline. This design ensures that if one microservice's build fails, the other parallel actions continue unaffected, as CodePipeline treats each action in a parallel group independently.

Answer

Configure the pipeline to block subsequent stages if any build action fails.

Answer

Configure a single build action that sequentially builds all microservices.

Question 4

A DevOps engineer is troubleshooting an application running on an EC2 instance. The application needs to access an Amazon RDS database using IAM database authentication. The EC2 instance is associated with an IAM role 'EC2-AppRole', and the RDS instance has a resource-based policy that allows 'DatabaseAccessRole' to connect. The engineer sees the error in the exhibit. What is the most likely cause?

Accepted Answer

The trust policy of the IAM role 'DatabaseAccessRole' does not allow the EC2 instance role 'EC2-AppRole' to assume it.. The error indicates that the EC2 instance's IAM role 'EC2-AppRole' cannot authenticate to the RDS instance. IAM database authentication requires the EC2 instance to assume a database authentication token, which is generated by calling the RDS API with the 'EC2-AppRole' credentials. However, the RDS instance's resource-based policy only allows 'DatabaseAccessRole' to connect. For 'EC2-AppRole' to successfully authenticate, it must first assume 'DatabaseAccessRole' via a trust policy that permits the EC2 instance role to assume it. Without this trust relationship, the authentication token request fails, causing the error.

Answer

The RDS instance does not have a resource-based policy that grants access to 'DatabaseAccessRole'.

Answer

The security group for the EC2 instance does not allow outbound traffic to the RDS instance.

Answer

The EC2 instance does not have the correct IAM instance profile attached.

Question 5

A company is running a critical application on an Amazon EC2 instance that needs to access an S3 bucket. The application must use temporary credentials that automatically rotate. The DevOps engineer must ensure that the credentials are never stored on disk. Which approach meets these requirements?

Accepted Answer

Attach an IAM role to the EC2 instance and use the instance profile to obtain temporary credentials from the instance metadata service.. Option B is correct because attaching an IAM role to the EC2 instance and using the instance profile allows the application to obtain temporary credentials from the EC2 instance metadata service (IMDS). These credentials are automatically rotated by AWS before they expire, and they are never stored on disk—they are fetched on-demand from the metadata endpoint (http://169.254.169.254/latest/meta-data/iam/security-credentials/). This satisfies both the requirement for automatic rotation and the prohibition against disk storage.

Answer

Store the credentials in AWS Secrets Manager and retrieve them at application startup.

Answer

Use AWS Systems Manager Parameter Store to store the credentials and retrieve them using the EC2 instance's IAM role.

Answer

Generate an access key and secret key for an IAM user and store them in a configuration file on the EC2 instance.

Question 6

A company has a requirement to rotate database credentials every 30 days for an Amazon RDS for MySQL instance. The credentials are currently stored in AWS Secrets Manager. The DevOps engineer needs to implement automatic rotation without modifying the application code. Which solution should be used?

Accepted Answer

Configure Secrets Manager to automatically rotate the secret every 30 days using a Lambda rotation function, and have the application retrieve the secret using the Secrets Manager API.. Option D is correct because AWS Secrets Manager natively supports automatic rotation of secrets using a Lambda function that updates both the secret in Secrets Manager and the password in the RDS MySQL instance. This solution meets the 30-day rotation requirement without modifying application code, as the application retrieves the current secret via the Secrets Manager API, which automatically handles versioning and caching.

Answer

Create a scheduled job that runs every 30 days to update the secret in Secrets Manager with a new password.

Answer

Store the credentials in AWS Systems Manager Parameter Store and configure automatic rotation using a Lambda function.

Answer

Use the AWS RDS automatic password rotation feature, which automatically updates the password every 30 days.

Question 7

A DevOps engineer manages infrastructure using Terraform. The team needs to store secrets such as database passwords in a secure manner and reference them in Terraform configurations. They have configured AWS Secrets Manager. What is the recommended approach to reference secrets in Terraform without exposing them in state files?

Accepted Answer

Use the 'data.aws_secretsmanager_secret_version' data source and mark the attribute as 'sensitive = true' in the output.. Option D is correct because using the `data.aws_secretsmanager_secret_version` data source retrieves the secret value at plan time without storing it in the Terraform state file. Marking the attribute as `sensitive = true` in the output prevents the value from being displayed in the CLI output, but the key protection is that the secret value itself is never written to the state file when using this data source — Terraform only stores the data source's ID and metadata, not the actual secret payload.

Answer

Store the secret ARN in a Terraform variable and use 'var.secret_arn' in the resource.

Answer

Store the secret in AWS Systems Manager Parameter Store and reference it using 'data.aws_ssm_parameter'.

Answer

Pass the secret as an environment variable to Terraform and reference it with 'var.secret_value'.

Question 8

A company is designing a disaster recovery (DR) strategy for a stateless web application deployed on Amazon ECS with Fargate. The application is fronted by an Application Load Balancer (ALB) and uses Amazon ElastiCache for Redis for session state. The primary region is us-east-1. The DR plan requires a Recovery Point Objective (RPO) of 15 minutes and a Recovery Time Objective (RTO) of 30 minutes. Which solution meets these requirements with the LEAST operational overhead?

Accepted Answer

Deploy an ALB with a warm standby ECS service in us-west-2. Use Route 53 health checks to route traffic to the secondary region if primary fails. Use ElastiCache Global Datastore for Redis to replicate data across regions.. Option A is correct because it uses ElastiCache Global Datastore for Redis, which provides cross-region replication with an RPO of seconds (well within 15 minutes) and automatic failover, minimizing operational overhead. The warm standby ECS service in us-west-2 with Route 53 health checks allows traffic to be redirected within the 30-minute RTO without manual intervention, as the ALB and ECS service are pre-provisioned.

Answer

Deploy an Active-Active configuration across two AWS regions using Route 53 latency routing. Use ElastiCache for Redis Global Datastore with multi-region writes.

Answer

Deploy a Pilot Light environment in us-west-2 with a scaled-down ECS service and Redis cluster. Use Route 53 DNS failover. On disaster, scale up the ECS service and promote the Redis cluster.

Answer

Use Amazon ECS with Fargate in us-east-1 only, and schedule daily snapshots of ElastiCache for Redis. In case of disaster, restore the snapshot in a new region and update DNS.

Question 9

A company runs a containerized microservices application on Amazon EKS. The application includes a critical service that processes real-time financial transactions. This service must be highly available and resilient to node failures. The current setup uses a Deployment with 3 replicas and a ClusterIP service. During a recent node failure, the application experienced a brief period of unavailability. Which action should the DevOps engineer take to improve resilience without changing the underlying infrastructure?

Accepted Answer

Configure a PodDisruptionBudget with a maxUnavailable of 1, and add pod anti-affinity rules to spread pods across different nodes.. Option C is correct because a PodDisruptionBudget with maxUnavailable=1 ensures that at most one pod is unavailable during voluntary disruptions, while pod anti-affinity rules force the scheduler to distribute pods across different nodes. This combination prevents a single node failure from taking down all replicas, maintaining service availability without altering the underlying infrastructure.

Answer

Change the service type from ClusterIP to NodePort and configure an external load balancer.

Answer

Increase the number of replicas to 10 and use a node selector to schedule all pods on the largest instance type.

Answer

Enable HorizontalPodAutoscaler with a target CPU utilization of 50% to automatically scale the Deployment.

Question 10

A company runs a stateful web application on EC2 instances behind a Network Load Balancer (NLB) in a single Availability Zone. The application stores session state locally on the instance. The company wants to achieve high availability across multiple AZs with minimal application changes. What should the DevOps engineer do?

Accepted Answer

Replace the NLB with an ALB and enable sticky sessions (session affinity) using the ALB's cookie.. Option D is correct because replacing the NLB with an ALB and enabling sticky sessions (session affinity) using the ALB's cookie allows the stateful web application to maintain session state across multiple AZs without modifying the application code. The ALB generates a cookie (AWSALB) that binds a client's session to a specific target instance, ensuring subsequent requests from the same client are routed to the same EC2 instance. This achieves high availability across AZs with minimal changes, as the application continues to store session state locally on the instance.

Answer

Add more AZs and configure the NLB with cross-zone load balancing.

Answer

Replace the NLB with an ALB and use ElastiCache for session storage.

Answer

Use a Multi-AZ RDS instance to store session state.

Question 11

A company runs a critical application on AWS using Amazon EC2 instances in an Auto Scaling group, an Application Load Balancer (ALB), and an Amazon RDS for PostgreSQL Multi-AZ DB cluster. The application must maintain an RTO of 5 minutes and an RPO of 1 second for database transactions. The current setup meets these requirements, but the DevOps team wants to improve the resilience of the application tier to withstand a regional failure. Which THREE actions should be taken? (Choose three.)

Accepted Answer

Replace the RDS Multi-AZ cluster with Amazon Aurora Global Database to replicate data across regions.. Amazon Aurora Global Database is the correct choice because it provides cross-region replication with a typical RPO of 1 second and RTO of 1 minute, meeting the stated requirements. Unlike standard RDS Multi-AZ, which is limited to a single region, Aurora Global Database replicates data asynchronously across multiple regions with minimal lag, ensuring the database tier can survive a regional failure while maintaining the required RPO of 1 second.

Answer

Use Amazon EFS Replication to replicate application data across regions with a recovery point objective (RPO) of 1 second.

Answer

Extend the existing Auto Scaling group to launch instances in two regions by specifying a second region in the launch template.

Question 12

A company runs a critical application on Amazon ECS with Fargate. The application experiences intermittent slow responses. The DevOps team enabled Container Insights and CloudWatch ServiceLens. However, traces from the application do not appear in ServiceLens. The application uses the AWS X-Ray SDK for tracing. What is the MOST likely cause?

Accepted Answer

The X-Ray daemon is not running in the task definition.. The X-Ray daemon is required to act as a local intermediary that receives trace segments from the X-Ray SDK and forwards them to the AWS X-Ray API. In Amazon ECS with Fargate, the daemon must be explicitly included as a sidecar container in the task definition. Without it, the SDK cannot send traces, which explains why traces are missing from ServiceLens despite the SDK being integrated.

Answer

The X-Ray SDK cannot send traces to AWS X-Ray from Fargate tasks.

Answer

ServiceLens does not support Amazon ECS with Fargate launch type.

Answer

The application is not sending metrics to CloudWatch Container Insights.

Question 13

A DevOps engineer is designing a deployment pipeline for a serverless application using AWS SAM. The pipeline must include the following stages: source, build, deploy to a development environment, run integration tests, and promote to production after manual approval. Which AWS services and features should be used to implement this pipeline? (Choose two.)

Accepted Answer

AWS CodePipeline to orchestrate the pipeline stages.. AWS CodePipeline is the correct service for orchestrating the pipeline stages because it provides native support for defining source, build, deploy, test, and manual approval stages in a sequential workflow. It integrates directly with AWS SAM and can trigger builds and deployments based on source code changes, making it the ideal orchestrator for this multi-stage pipeline.

Answer

AWS CodeDeploy for deploying the SAM application.

Answer

AWS CodeCommit to build the SAM application.

Question 14

A company runs a web application on Amazon EC2 instances behind an Application Load Balancer. The DevOps team has enabled detailed CloudWatch metrics for the ALB and is using CloudWatch Logs for the EC2 instances. Recently, users report intermittent 503 errors. The team notices that the ALB's 'RequestCount' metric shows a sudden drop during error periods, while the 'ActiveConnectionCount' remains steady. Which TWO steps should the team take to diagnose the issue? (Choose two.)

Accepted Answer

Enable and analyze the ALB access logs to see the HTTP response codes and target processing time.. Option A is correct because ALB access logs contain detailed per-request data, including HTTP response codes (e.g., 503) and target processing time. Analyzing these logs will reveal whether the 503 errors are coming from the ALB itself (e.g., due to request queue overflow) or from the targets, and whether the sudden drop in RequestCount is due to clients aborting or the ALB throttling requests.

Answer

Check the Amazon Route 53 health checks for the ALB DNS name.

Answer

Review the EC2 instances' CloudWatch metrics for CPU utilization and network traffic.

Answer

Inspect AWS CloudTrail logs for the ALB to see if there are any configuration changes.

Question 15

A DevOps engineer receives the error shown in the exhibit when attempting to update an existing CloudFormation stack that deploys a VPC with subnets. The stack was created successfully earlier using the same template. What is the most likely cause of this error?

Accepted Answer

The IAM role used for the stack update lacks the 'ec2:DescribeSubnets' permission.. When updating a CloudFormation stack that deploys a VPC with subnets, the update operation must be able to read the current state of the subnet resources to determine if changes are needed. The IAM role used for the stack update must have the 'ec2:DescribeSubnets' permission to query the existing subnet configuration. Without this permission, CloudFormation cannot verify the subnet's current properties, leading to the error shown in the exhibit.

Answer

The subnet ID in the template is already used by another stack in the same account.

Answer

The subnet specified in the template does not exist in the selected AWS region.

Answer

The CloudFormation template has a syntax error in the subnet definition.

Question 16

A company uses AWS CodeCommit as a source repository and wants to enforce that all commits are signed using GPG keys. The DevOps team configures a pre-receive hook in CodeCommit to validate commit signatures. However, the hook rejects all commits even when valid GPG signatures are present. What is the most likely cause?

Accepted Answer

CodeCommit does not support pre-receive hooks.. AWS CodeCommit does not support pre-receive hooks. Pre-receive hooks are a feature of self-managed Git repositories (e.g., GitHub Enterprise, GitLab, or on-premises Git servers) that run on the server before accepting a push. CodeCommit uses IAM policies and repository-level settings (such as requiring signed commits via the 'git push --signed' flag) to enforce commit signing, not server-side hooks. Therefore, any attempt to configure a pre-receive hook in CodeCommit will fail, causing all commits to be rejected.

Answer

The GPG key is not registered with the IAM user's profile.

Answer

The hook script has a syntax error.

Answer

The repository is not configured to require signed commits.

Question 17

A company uses DynamoDB global tables in two AWS Regions with strong consistency reads. They observe occasional write conflicts that are not being resolved automatically. The application uses DynamoDBMapper with optimistic locking. What should the DevOps engineer do to ensure conflict resolution?

Accepted Answer

Use conditional writes with a version number attribute to ensure updates are applied only to the latest version.. Option D is correct because DynamoDB global tables use last-writer-wins (LWW) for conflict resolution by default, but when using DynamoDBMapper with optimistic locking, the application must implement conditional writes with a version number attribute to ensure updates are applied only to the latest version. This prevents stale updates from overwriting newer data, as the conditional write will fail if the version number in the request does not match the current version in the table, allowing the application to retry with the updated version.

Answer

Implement a custom conflict resolution using DynamoDB Streams and AWS Lambda.

Answer

Switch to eventual consistency reads to reduce conflicts.

Answer

Add a third global table region to increase redundancy.

Question 18

A company's application uses Amazon DynamoDB as its primary data store. The application experiences occasional throttling errors during traffic spikes. The DevOps team needs to implement a solution that ensures consistent performance without manual intervention. Which TWO actions should the team take? (Choose TWO.)

Accepted Answer

Implement DynamoDB Accelerator (DAX) to cache read requests.. DynamoDB Accelerator (DAX) is an in-memory cache that reduces read response times from milliseconds to microseconds, offloading read-heavy workloads from the DynamoDB table. By caching frequently accessed items, DAX absorbs traffic spikes and reduces the likelihood of throttling on read requests, ensuring consistent performance without manual intervention.

Answer

Use eventually consistent reads for all queries.

Answer

Move the data to Amazon RDS with read replicas.

Answer

Switch DynamoDB to On-Demand capacity mode.

Question 19

A DevOps team is using Amazon CloudWatch Logs to collect application logs from multiple EC2 instances. They notice that some log entries are missing and that the CloudWatch agent is consuming high CPU. The log group has a retention policy of 30 days. Which action should the team take to reduce CPU usage without losing log data?

Accepted Answer

Increase the batch size in the CloudWatch agent configuration.. Increasing the batch size in the CloudWatch agent configuration reduces the number of HTTP API calls made to CloudWatch Logs, which lowers CPU overhead from frequent network I/O and serialization. The agent buffers log events and sends them in larger, less frequent batches, directly addressing high CPU consumption without discarding any log data.

Answer

Use JSON format for logs instead of plain text.

Answer

Set the agent's timezone to UTC.

Answer

Change the log group retention policy to 7 days.

Question 20

A company is using Amazon CloudWatch Synthetics canaries to monitor its web application endpoints. The canaries are deployed in multiple AWS regions. The team wants to aggregate the canary results into a single dashboard in the US East (N. Virginia) region. What is the MOST efficient way to achieve this?

Accepted Answer

Create a cross-region CloudWatch dashboard and add metrics from each region using metric math.. Option B is correct because CloudWatch cross-region dashboards allow you to aggregate metrics from multiple regions into a single dashboard without data movement. By using metric math, you can reference metric IDs from different regions directly in the dashboard widget, enabling real-time aggregation of Synthetics canary success/failure rates and latency metrics from all regions into a unified view in US East (N. Virginia). This approach avoids unnecessary data replication, reduces latency, and minimizes operational overhead.

Answer

Replicate the canaries to US East (N. Virginia) and run them from there.

Answer

Set up a Lambda function in each region to push canary results to a central S3 bucket, then create a dashboard from S3.

Answer

Create a CloudWatch Logs Insights query across all regions and visualize results.