DOP-C02 Resilient Cloud Solutions Practice Test 2 — 15 Questions

Question 1

A company is building a multi-tier web application on AWS. The application must be resilient to the failure of an entire Availability Zone. The architecture includes an Application Load Balancer (ALB), EC2 instances in an Auto Scaling group, and an Amazon RDS for MySQL database. Which TWO actions should be taken to achieve this resilience? (Choose two.)

Accepted Answer

Configure the Auto Scaling group to launch EC2 instances in at least two Availability Zones.. Option D is correct because configuring the Auto Scaling group to launch EC2 instances in at least two Availability Zones ensures that if one AZ fails, the remaining AZ(s) can continue serving traffic. This is a fundamental pattern for building AZ-resilient compute tiers. Option E is correct because deploying Amazon RDS for MySQL in a Multi-AZ configuration automatically provisions and maintains a synchronous standby replica in a different AZ, providing automatic failover if the primary DB instance fails, thus ensuring database resilience.

Answer

Configure an RDS read replica in a different Availability Zone.

Answer

Use a Single-AZ RDS for MySQL database to keep costs low.

Answer

Place all EC2 instances in the same Availability Zone to reduce cross-AZ data transfer costs.

Question 2

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 3

A company runs a production e-commerce platform on AWS. The architecture includes an Application Load Balancer (ALB) that distributes traffic to a fleet of Amazon EC2 instances running in an Auto Scaling group across three Availability Zones (AZs). The application stores session state in Amazon ElastiCache for Redis (cluster mode disabled) with a single node. The database is an Amazon Aurora MySQL DB cluster with one writer and two reader instances in different AZs. The platform experiences intermittent slowdowns and occasional timeouts during peak traffic hours. The CloudWatch metrics show that the ALB's TargetResponseTime is elevated, and the Redis CPU utilization is consistently above 80% during these periods. The Auto Scaling group is scaling out, but new instances take several minutes to become healthy. The DevOps team has been asked to improve the resilience and performance of the application with minimal changes to the application code. Which solution should the team implement?

Accepted Answer

Migrate ElastiCache for Redis to a cluster mode enabled configuration with multiple shards and enable Multi-AZ with automatic failover. Also, use an ElastiCache replication group with read replicas in different AZs.. Option D is correct because the primary bottleneck is the single-node Redis instance (CPU > 80%), which cannot scale reads or handle failover. Migrating to cluster mode enabled with multiple shards distributes the CPU load across shards, while Multi-AZ with automatic failover and read replicas in different AZs provides high availability and read scaling. This directly addresses the elevated ALB TargetResponseTime caused by Redis latency without requiring application code changes.

Answer

Replace the ALB with a Network Load Balancer (NLB) to reduce latency, and use an Auto Scaling group with a step scaling policy based on Redis CPU utilization.

Answer

Increase the instance size of the ElastiCache for Redis node and the size of the Aurora writer instance. Also, increase the cooldown period for the Auto Scaling group to allow new instances to warm up.

Answer

Implement Amazon RDS Proxy in front of the Aurora cluster to reduce database connection overhead, and increase the size of the Redis instance to handle more connections.

Question 4

A company runs a critical web application on Amazon EC2 instances behind an Application Load Balancer (ALB) across multiple Availability Zones. The application stores session data in a shared Amazon ElastiCache for Redis cluster. The operations team reports that during a recent AZ failure, users experienced session loss and application errors. Which combination of actions should the company take to improve resilience and maintain session state during an AZ failure? (Choose TWO.)

Accepted Answer

Configure the ALB with cross-zone load balancing enabled and connection draining set to a suitable timeout.. Option A is correct because enabling cross-zone load balancing on the ALB ensures traffic is distributed evenly across all EC2 instances in all AZs, and connection draining with a suitable timeout allows in-flight requests to complete before instances are deregistered, preventing session loss during an AZ failure. Option C is correct because enabling cluster mode for ElastiCache for Redis with replica nodes in different AZs provides automatic sharding and replication, ensuring session data remains available and consistent even if a primary node in one AZ fails.

Answer

Deploy an Auto Scaling group with a dynamic scaling policy that adds instances in the remaining AZs.

Answer

Configure the application to use a custom DNS name with a low TTL pointing to the ElastiCache cluster endpoint.

Answer

Enable Multi-AZ for the ElastiCache cluster to automatically fail over to a replica in another AZ.

Question 5

An AWS Lambda function that processes sensitive data writes objects to an S3 bucket. The security team requires that all objects be encrypted at rest using SSE-S3. The Lambda execution role uses the above IAM policy. Despite the policy, some objects are uploaded without server-side encryption. What is the most likely cause?

Accepted Answer

The Lambda function does not include the x-amz-server-side-encryption header in the PutObject request.. Option A is correct because the IAM policy only allows the PutObject action when the request includes the `x-amz-server-side-encryption` header set to `AES256` (SSE-S3). If the Lambda function omits this header in its PutObject call, the request does not satisfy the IAM condition key `s3:x-amz-server-side-encryption`, and the policy denies the upload. However, the question states that objects are uploaded without encryption, which implies the policy is not being enforced as intended—likely because the Lambda function is not including the required header, and the bucket's default encryption or another mechanism is allowing the upload to succeed despite the policy.

Answer

The bucket has a default encryption policy that overrides the IAM policy.

Answer

The Lambda function is using a KMS key instead of SSE-S3.

Answer

The Lambda function is specifying a different encryption algorithm, such as aws:kms.

Question 6

A company runs a stateless web application on EC2 instances in an Auto Scaling group across three Availability Zones. The application uses an Application Load Balancer. The operations team needs to ensure that the application remains available if one AZ fails. Which solution is MOST resilient?

Accepted Answer

Configure the Auto Scaling group to launch instances in three Availability Zones with a desired capacity of 3.. Option C is correct because distributing instances across three Availability Zones (AZs) with a desired capacity of 3 ensures that even if one AZ fails, the remaining two AZs still have at least 2 instances running, maintaining service capacity. The Application Load Balancer (ALB) automatically routes traffic away from the failed AZ, and the Auto Scaling group will replace lost instances in the healthy AZs, providing the highest resilience against a single-AZ failure.

Answer

Configure the Auto Scaling group to launch instances in a single Availability Zone with a desired capacity of 6.

Answer

Configure the Auto Scaling group to launch instances in two Availability Zones with a desired capacity of 4.

Answer

Configure the Auto Scaling group to launch instances in two Availability Zones with a desired capacity of 6, all in one AZ.

Question 7

Drag and drop the steps to troubleshoot a failed deployment in AWS CodeDeploy into the correct order.

Question 8

Drag and drop the steps to perform a disaster recovery failover from a primary region to a secondary region using AWS Route 53 and RDS.

Question 9

Match each AWS CloudFormation concept to its description.

Question 10

Match each AWS CLI command to its function.

Question 11

A company runs a critical web application on EC2 instances behind an Application Load Balancer (ALB). The application stores session state in an Amazon DynamoDB table. During a recent traffic spike, users experienced session timeouts and the application became unavailable. Which design change would BEST improve resilience?

Accepted Answer

Enable DynamoDB global tables or use a Multi-AZ deployment for the table.. Option C is correct because using a Multi-AZ deployment for DynamoDB provides automatic failover and higher availability. Option A is wrong because increasing instance size does not address session state persistence. Option B is wrong because read replicas do not improve write availability. Option D is wrong because ElastiCache for Redis is not as resilient as DynamoDB Multi-AZ for session state.

Answer

Move session state to Amazon ElastiCache for Redis with cluster mode disabled.

Answer

Add a read replica to the DynamoDB table.

Answer

Increase the EC2 instance sizes to handle more traffic.

Question 12

A company runs a stateless web application on AWS Lambda behind an Application Load Balancer (ALB). During a deployment, the team updates the Lambda function to a new version. Some users report seeing the old version of the application for several minutes after the deployment. What is the MOST likely cause?

Accepted Answer

The ALB target group is still pointing to the old Lambda function version due to connection draining.. Option B is correct because ALB has a warm-up effect and may keep old connections alive, causing traffic to old Lambda versions if the alias is not updated atomically. Option A is wrong because Lambda versions are immutable. Option C is wrong because CloudFront caching is unrelated to ALB. Option D is wrong because Lambda@Edge is not involved in this setup.

Answer

The Lambda function versions are not immutable, causing a gradual rollout.

Answer

Lambda@Edge is overriding the function version at the edge locations.

Answer

Amazon CloudFront is caching the old response and has not been invalidated.

Question 13

A company is designing a disaster recovery strategy for its primary RDS for PostgreSQL database in us-east-1. The RTO is 15 minutes and RPO is 1 minute. Which solution meets these requirements?

Accepted Answer

Create a cross-Region read replica in the secondary Region and promote it during failover.. Option C is correct because a cross-Region read replica can be promoted to a primary instance quickly, meeting both RTO and RPO. Option A is wrong because manual snapshots have a higher RPO. Option B is wrong because Multi-AZ is only within a region. Option D is wrong because automated backups alone do not enable cross-Region failover.

Answer

Use AWS Backup to copy automated backups to the secondary Region every hour.

Answer

Deploy a Multi-AZ RDS instance and failover to the standby in the same region.

Answer

Take manual snapshots of the database every 5 minutes and copy them to the secondary Region.

Question 14

A company runs a microservices application on Amazon ECS with Fargate launch type. The application experiences intermittent failures when calling an external API. The errors are transient and usually resolve within a few seconds. How should the company improve resilience?

Accepted Answer

Implement retry logic with exponential backoff in the application code.. Option B is correct because implementing retry logic with exponential backoff handles transient failures gracefully. Option A is wrong because scaling up may not help with API failures. Option C is wrong because increasing timeouts could worsen latency. Option D is wrong because async processing adds complexity and does not directly address API failures.

Answer

Increase the timeout of the external API call to 60 seconds.

Answer

Increase the number of tasks in the ECS service to handle failures.

Answer

Use an Amazon SQS queue to decouple the API call from the application.

Question 15

A company uses AWS CloudFormation to deploy a multi-tier application. During an update, the stack fails and rolls back. The rollback also fails, leaving the stack in UPDATE_ROLLBACK_FAILED state. The operations team needs to resolve this with minimal disruption. What is the MOST efficient approach?

Accepted Answer

Use the 'ContinueUpdateRollback' API or AWS Management Console to retry the rollback.. Option A is correct because continuing the rollback can resolve the failure and bring the stack to a consistent state. Option B is wrong because deleting the stack would remove all resources. Option C is wrong because executing a change set on a failed stack is not possible. Option D is wrong because manual modification is error-prone and not recommended.

Answer

Manually modify the resources to match the previous stack state.

Answer

Delete the stack and recreate it from the original template.

Answer

Execute a change set to update the stack to the desired configuration.