DOP-C02 Resilient Cloud Solutions Practice Test 14 — 15 Questions

Question 1

A company runs a critical web application on EC2 instances in an Auto Scaling group. The application uses an Application Load Balancer (ALB) with health checks pointing to /health. Recently, the application experienced intermittent failures where the ALB would mark instances as unhealthy and route traffic away, causing a reduction in capacity. The development team noticed that the /health endpoint occasionally returns HTTP 503 when the application is under heavy load, but the application can recover quickly. The team wants to avoid unnecessary instance replacements while ensuring availability. Which solution should the DevOps engineer implement?

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

Accepted Answer

Increase the health check interval and increase the unhealthy threshold. Increasing the health check interval and increasing the unhealthy threshold makes the health check less sensitive to transient errors, such as occasional 503 responses under heavy load. This prevents unnecessary instance replacements while maintaining availability. Option A is incorrect because implementing a custom Lambda health check that ignores 503 responses would not leverage the built-in ALB health check tuning and adds complexity. Option B is incorrect because decreasing the unhealthy threshold would make instances more easily marked unhealthy, worsening the problem. Option D is incorrect because decreasing the health check interval increases the frequency of checks, which might cause more frequent detections of transient errors, and decreasing the healthy threshold does not address the issue of avoiding unnecessary replacements.

Answer

Implement a custom health check using Lambda that ignores 503 responses

Answer

Decrease the unhealthy threshold to mark instances unhealthy faster

Answer

Decrease the health check interval and decrease the healthy threshold

Question 2

A company has deployed a multi-tier application on AWS. The web tier uses an Auto Scaling group of EC2 instances behind an Application Load Balancer. The application tier uses another Auto Scaling group of EC2 instances that process messages from an Amazon SQS queue. The database tier uses Amazon RDS Multi-AZ. Recently, the application experienced a complete outage when the SQS queue became overwhelmed with messages due to a sudden spike in traffic. The application tier could not process messages fast enough, causing the queue to grow indefinitely and eventually exceed the visibility timeout, leading to message loss and degraded performance. The DevOps engineer needs to improve the resilience of the architecture to handle traffic spikes without losing messages. Which solution should be implemented?

Accepted Answer

Configure a dead-letter queue for unprocessed messages and implement Auto Scaling based on SQS queue depth. It addresses both the message loss and processing bottleneck. A dead-letter queue (DLQ) captures messages that cannot be processed successfully after a specified number of attempts, preventing them from being lost when the visibility timeout expires. Implementing Auto Scaling based on SQS queue depth (using a CloudWatch alarm on the ApproximateNumberOfMessagesVisible metric) dynamically adds more application-tier EC2 instances when the queue grows, ensuring the processing rate scales with demand and prevents the queue from being overwhelmed.

Answer

Limit the maximum message size and set a queue size limit to prevent overflow

Answer

Replace the standard SQS queue with a FIFO SQS queue to ensure exactly-once processing

Answer

Increase the visibility timeout in the SQS queue to allow more time for processing

Question 3

A DevOps team is designing a disaster recovery plan for an RDS MySQL database. The database must be recoverable with minimal data loss in case of a regional failure. Which solution provides the LOWEST Recovery Point Objective (RPO)?

Accepted Answer

Configure a Cross-Region Read Replica.. A Cross-Region Read Replica provides the lowest Recovery Point Objective (RPO) because it uses asynchronous replication to continuously replicate data changes from the primary region to a replica in another region. In the event of a regional failure, you can promote the replica to a standalone primary database, typically losing only a few seconds to minutes of data, depending on replication lag. This minimizes data loss compared to snapshot-based or batch replication methods.

Answer

Take daily automated snapshots and copy them to another Region.

Answer

Use a Multi-AZ deployment with synchronous standby.

Answer

Use RDS Proxy to cache database writes.

Question 4

A company runs a stateless web application on Amazon ECS with Fargate. The application must be highly available across multiple Availability Zones. What is the BEST way to achieve this?

Accepted Answer

Create an ECS service with tasks in multiple AZs and place an ALB in front.. Running an ECS service with tasks in multiple Availability Zones (AZs) and placing an Application Load Balancer (ALB) in front ensures that if one AZ becomes unavailable, the ALB can route traffic to healthy tasks in the remaining AZs. This architecture provides both high availability and fault tolerance for the stateless web application, as the ALB performs health checks and distributes requests across tasks in different AZs.

Answer

Use an Auto Scaling group of EC2 instances in a single AZ and run ECS tasks on them.

Answer

Deploy a CloudFront distribution with multiple origins in different AZs.

Answer

Deploy a single ECS service with tasks in one AZ and use an ALB.

Question 5

A company's application runs on Amazon EC2 instances in an Auto Scaling group. The application writes logs to local instance storage. The operations team needs to ensure logs are not lost during instance termination or scaling events. What should be done?

Accepted Answer

Install the CloudWatch Logs agent on each instance and stream logs to CloudWatch Logs.. The CloudWatch Logs agent streams log data in near real-time to Amazon CloudWatch Logs, ensuring logs are persisted independently of the EC2 instance lifecycle. This decouples log storage from ephemeral instance store volumes, so logs are not lost during Auto Scaling termination or scaling events. The agent handles log rotation, compression, and encryption in transit, providing a durable and centralized log solution.

Answer

Increase the size of the instance store volumes.

Answer

Use an Amazon EFS file system and mount it to each instance for log storage.

Answer

Configure the Auto Scaling group to terminate instances after logs are copied to S3.

Question 6

A company uses Amazon Route 53 for DNS. They want to ensure that if their primary website endpoint fails, traffic is automatically routed to a secondary endpoint in a different Region. Which routing policy should be used?

Accepted Answer

Failover routing. Failover routing policy allows you to configure an active-passive failover setup.

Answer

Latency routing

Answer

Simple routing

Answer

Weighted routing

Question 7

A company is building a serverless application using AWS Lambda, Amazon API Gateway, and Amazon DynamoDB. The application must be resilient to sudden spikes in traffic without manual intervention. Which combination of services should be used?

Accepted Answer

API Gateway with throttling, Lambda with reserved concurrency, and DynamoDB auto scaling.. It combines API Gateway throttling to absorb traffic spikes by queuing or rejecting excess requests, Lambda reserved concurrency to guarantee execution capacity for the function, and DynamoDB auto scaling to adjust read/write capacity based on demand. This triad ensures the application remains available and responsive under sudden load without manual intervention.

Answer

API Gateway with usage plans, Lambda with provisioned concurrency, and DynamoDB on-demand.

Answer

API Gateway with WAF, Lambda with function URLs, and DynamoDB Accelerator (DAX).

Answer

API Gateway with caching, Lambda with no concurrency limits, and DynamoDB global tables.

Question 8

A company runs a containerized application on Amazon EKS. The application must be highly available across multiple Availability Zones and must automatically recover from node failures. Which THREE steps should be taken?

Accepted Answer

Use Pod Disruption Budgets to ensure a minimum number of pods are available during voluntary disruptions.. Pod Disruption Budgets (PDBs) are correct because they allow you to specify the minimum number of pods that must remain available during voluntary disruptions, such as node drains or cluster upgrades. This ensures that the application maintains high availability even when Kubernetes performs planned maintenance, preventing all replicas from being taken down simultaneously.

Answer

Deploy worker nodes in a single Availability Zone to reduce cross-AZ data transfer costs.

Answer

Use a single large instance type for all worker nodes to simplify management.

Question 9

A company wants to ensure that its Amazon S3 bucket is resilient to accidental deletion of objects. Which TWO actions should be taken?

Accepted Answer

Enable MFA Delete on the bucket.. Enabling MFA Delete on an S3 bucket requires multi-factor authentication for any delete operations, including object version deletion and bucket deletion. This adds a critical layer of protection against accidental or unauthorized deletions, as the user must present both their AWS credentials and a valid MFA code to perform these destructive actions.

Answer

Enable S3 Object Lock.

Answer

Enable S3 Transfer Acceleration.

Answer

Configure a lifecycle policy to expire objects after 30 days.

Question 10

Refer to the exhibit. An IAM policy is attached to an IAM role used by an EC2 instance. The instance is part of an Auto Scaling group. During a scale-in event, the instance fails to stop itself. What is the MOST likely cause?

Accepted Answer

The policy does not allow ec2:TerminateInstances.. During a scale-in event, the Auto Scaling group must terminate the EC2 instance. The IAM policy attached to the instance's role must include ec2:TerminateInstances permission for the instance to successfully stop itself. Without this permission, the instance cannot be terminated, causing the scale-in action to fail.

Answer

The policy allows ec2:StopInstances but not ec2:StartInstances.

Answer

The policy does not allow ec2:DescribeInstanceStatus.

Answer

The policy does not allow ec2:ModifyInstanceAttribute.

Question 11

A company runs a high-traffic web application on a fleet of EC2 instances behind an Application Load Balancer (ALB) with Auto Scaling. The application uses an Amazon RDS for PostgreSQL database. Recently, during a traffic spike, the application became unresponsive. Investigation revealed that the database CPU utilization reached 100%, causing queries to timeout. The Auto Scaling group added more EC2 instances, which only increased the load on the database. The DevOps team needs to implement a solution that prevents the database from being overwhelmed during traffic spikes while maintaining application availability. The solution must be cost-effective and require minimal changes to the application code. Which solution should the DevOps team implement?

Accepted Answer

Use Amazon RDS Proxy between the application and the database to pool and reuse connections.. RDS Proxy manages database connections efficiently, reducing the number of connections and CPU overhead. It also provides connection pooling, which helps handle spikes without overwhelming the database.

Answer

Implement read replicas for the RDS database and modify the application to use read replicas for read queries.

Answer

Increase the instance size of the RDS database to a larger instance type to handle more connections.

Answer

Configure Auto Scaling to launch EC2 instances based on a custom metric that tracks database CPU utilization, and throttle the number of instances.

Question 12

A company hosts a static website on Amazon S3 with a CloudFront distribution. The website is critical for business operations and must be available even if the primary AWS Region fails. Currently, the S3 bucket is in us-east-1, and CloudFront uses that bucket as the origin. The company has a secondary bucket in us-west-2 with a replica of the data. The company wants to use CloudFront to automatically fail over to the secondary bucket if the primary becomes unavailable. The DevOps engineer needs to implement a solution that requires minimal operational overhead. What should the engineer do?

Accepted Answer

Configure CloudFront Origin Failover by adding both buckets as origins, with the primary in us-east-1 and secondary in us-west-2.. CloudFront Origin Failover allows you to set up a primary and secondary origin. If the primary returns an error (e.g., 503), CloudFront automatically routes requests to the secondary origin.

Answer

Use an Application Load Balancer in front of both S3 buckets and point CloudFront to the ALB.

Answer

Create a second CloudFront distribution pointing to the secondary bucket and use Route 53 failover routing between the two distributions.

Answer

Modify the application to switch the CloudFront origin URL using Lambda@Edge when health checks fail.

Question 13

A company uses AWS CloudFormation to deploy infrastructure. During a recent deployment, the stack failed to create an Amazon RDS DB instance because of a parameter validation error. The DevOps engineer fixed the parameter and wants to resume the stack creation without recreating the resources that were already successfully created. The stack template is parameterized and uses nested stacks. What is the MOST efficient way to resume the stack creation?

Accepted Answer

Use the CloudFormation stack update operation with the corrected parameter.. CloudFormation stack updates can be used to fix the issue. By updating the stack with the corrected parameters, CloudFormation will only modify the failed resource and not recreate already created resources.

Answer

Manually create the RDS instance with the corrected parameter and update the stack to import it.

Answer

Delete the entire stack and redeploy with the corrected parameter.

Answer

Use the 'ContinueUpdateRollback' feature to rollback the failed stack and then redeploy.

Question 14

A company runs a microservices application on Amazon ECS with Fargate. The application uses an Application Load Balancer (ALB) to route traffic to services. Each service has a required number of tasks for capacity. The company recently experienced a prolonged outage when a bug caused all tasks of the critical 'payment' service to crash simultaneously. The DevOps team needs to implement a deployment strategy that reduces the risk of a full service outage during updates. The strategy must also allow for quick rollback if a deployment fails. Which deployment strategy should the team implement?

Accepted Answer

Implement blue/green deployment using ECS with target tracking alarms to automate traffic shifting.. Blue/green deployment with target tracking allows you to gradually shift traffic to the new version while monitoring. If issues arise, you can instantly rollback by switching traffic back to the old version.

Answer

Implement a rolling update with a fixed number of tasks to replace at a time.

Answer

Use a canary deployment by creating a new service with a small number of tasks, test, then shift all traffic.

Answer

Deploy changes during maintenance windows with manual approval steps.

Question 15

A media company runs a video processing pipeline on AWS. Raw videos are uploaded to an S3 bucket, which triggers a Lambda function to start an AWS Batch job for transcoding. The Batch job reads the source video from S3, processes it, and writes the output to another S3 bucket. Recently, the company has seen an increase in processing failures. Investigation shows that the Batch jobs are being terminated with a 'TIMEOUT' status after running for exactly 30 minutes. The video files are large, and some jobs legitimately take up to 45 minutes. The Batch job definition has a 'timeout' setting configured. Which action should be taken to resolve this issue?

Accepted Answer

Modify the Batch job definition to increase the 'timeout' value to 3600 seconds (60 minutes).. The timeout configured in the job definition is causing jobs that exceed 30 minutes to be terminated. Increasing the timeout to 60 minutes allows longer-running jobs to complete.

Answer

Increase the S3 bucket lifecycle policy to retain videos longer.

Answer

Increase the Lambda function timeout to 60 minutes.

Answer

Change the Batch job queue to a different compute environment.