DOP-C02 Resilient Cloud Solutions Practice Test 6 — 15 Questions

Question 1

A company uses AWS Lambda to process messages from an SQS queue. They need to ensure that if the Lambda function fails, the message is not lost and can be processed again. Which configuration is required?

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

Accepted Answer

Set the Lambda event source mapping to not delete messages from the queue on failure.. The Lambda event source mapping for SQS can be configured to not delete messages from the queue if the function fails. This ensures that the message remains in the queue and becomes visible again after the visibility timeout expires, allowing it to be retried. Without this setting, Lambda automatically deletes messages upon successful processing, but on failure, the default behavior is to delete them as well, which would cause message loss.

Answer

Set the visibility timeout to less than the Lambda function timeout.

Answer

Enable SQS redrive policy to retry messages.

Answer

Configure a dead-letter queue (DLQ) on the SQS queue.

Question 2

A company runs a critical application on EC2 instances in an Auto Scaling group behind an ALB. They want to ensure that if an instance fails, the application remains available with minimal disruption. Which combination of services provides the best resilience?

Accepted Answer

Auto Scaling group with ELB health checks and multiple AZs.. Deploying an Auto Scaling group across multiple Availability Zones (AZs) with Elastic Load Balancer (ALB) health checks ensures that if an EC2 instance fails in one AZ, the ALB automatically routes traffic to healthy instances in other AZs, and Auto Scaling replaces the failed instance. This combination provides both fault isolation and automated recovery, minimizing disruption to the application.

Answer

Auto Scaling group with minimum 2 in a single AZ.

Answer

EC2 instance recovery with CloudWatch alarms.

Answer

Auto Scaling group with desired capacity of 2 and a lifecycle hook.

Question 3

A company wants to design a resilient architecture for a web application using AWS services. Which of the following is a best practice for improving resilience?

Accepted Answer

Deploy EC2 instances in multiple Availability Zones.. Deploying EC2 instances across multiple Availability Zones (AZs) is a fundamental best practice for resilience because it eliminates a single point of failure at the data center level. If one AZ experiences an outage, traffic can be automatically routed to healthy instances in other AZs via an Elastic Load Balancer (ELB), ensuring application availability. This approach aligns with the AWS Well-Architected Framework's Reliability Pillar, which mandates distributing workloads across multiple AZs to achieve high availability.

Answer

Use an Auto Scaling group in a single AZ.

Answer

Use a single AZ with RDS Multi-AZ.

Answer

Use one large EC2 instance to handle all traffic.

Question 4

A company is designing a multi-region disaster recovery strategy for a stateless web application. They want to minimize RTO and RPO. Which TWO of the following should they implement? (Choose TWO.)

Accepted Answer

Use cross-region replication for data stores.. Cross-region replication for data stores ensures that data is continuously synchronized to a secondary AWS region, minimizing Recovery Point Objective (RPO) to near-zero and reducing Recovery Time Objective (RTO) as the data is already available in the DR region. This approach avoids the need to restore from backups, which would increase RTO and potentially lose recent transactions.

Answer

Use a passive standby in a single Availability Zone.

Answer

Perform periodic backups and restore in the DR region.

Answer

Configure cross-region read replicas for the database.

Question 5

A company uses Amazon ECS with Fargate for containerized applications. They need to ensure that if a task fails, it is automatically restarted and the application remains available. Which THREE actions should they take? (Choose THREE.)

Accepted Answer

Configure the ECS service to automatically restart failed tasks.. Amazon ECS services can be configured with a desired task count and a task placement strategy that automatically replaces any failed or stopped tasks. When a task exits unexpectedly, the ECS service scheduler detects the discrepancy between the desired and running count and launches a new task to maintain availability. This is the native mechanism for self-healing in ECS, without requiring external triggers.

Answer

Set up a CloudWatch alarm to trigger AWS Lambda to restart tasks.

Answer

Configure an EC2 Auto Scaling group for the ECS cluster.

Question 6

A company runs a mission-critical database on Amazon RDS for MySQL. They need to ensure that if the primary DB instance fails, the database remains available with minimal downtime. Which TWO configurations should they implement? (Choose TWO.)

Accepted Answer

Create a read replica in the same region.. For minimal downtime during a primary DB instance failure, Multi-AZ deployment (D) provides automatic failover to a standby in a different Availability Zone. A read replica in the same region (B) can be manually promoted to a primary instance, offering a faster failover option than restoring from backups. Automated backups (A) enable point-in-time recovery but do not reduce downtime due to restore time. Deletion protection (C) prevents accidental deletion, and cross-region replication (E) is for disaster recovery, not immediate failover.

Answer

Enable automated backups with point-in-time recovery.

Answer

Enable deletion protection on the DB instance.

Answer

Configure cross-region replication.

Question 7

Refer to the exhibit. An IAM policy is attached to a user. A developer tries to upload an object to s3://my-bucket/confidential/report.pdf without specifying server-side encryption. What will happen?

Accepted Answer

The upload fails because the Deny statement requires SSE-KMS.. The upload fails because the Deny statement in the IAM policy explicitly denies the s3:PutObject action unless the request includes the s3:x-amz-server-side-encryption header with a value of 'aws:kms'. When the developer does not specify server-side encryption, the condition is not met, so the Deny applies, causing the upload to fail. Option A is incorrect because the Allow statement does not override an explicit Deny. Option B is incorrect because the condition key is correct; the failure is due to the missing encryption header. Option D is incorrect because the Deny is not based on the object name prefix; it applies to all objects in the bucket.

Answer

The upload succeeds because the Allow statement grants PutObject.

Answer

The upload succeeds because the Deny condition uses a wrong condition key.

Answer

The upload fails only if the object name matches the prefix.

Question 8

A company runs a high-traffic e-commerce application on EC2 instances in an Auto Scaling group behind an ALB. The application uses an in-memory cache on the EC2 instances. During a recent deployment, the Auto Scaling group terminated an instance that had active user sessions, causing users to lose their cart data and leading to a poor customer experience. The company wants to prevent this in future deployments. They need a solution that allows existing sessions to complete before instance termination, without manual intervention. Which solution should they use?

Accepted Answer

Implement an Auto Scaling lifecycle hook that puts the instance in a 'terminating:wait' state, and have a script on the instance that signals completion after draining sessions.. Lifecycle hooks allow the Auto Scaling group to wait for a specified timeout before terminating an instance, giving the application time to drain sessions. Option A is incorrect because connection draining on the ALB only handles HTTP connections, not application-level session state. Option B is incorrect because increasing cooldown does not delay termination. Option D is incorrect because updating the health check type does not prevent immediate termination.

Answer

Increase the Auto Scaling group's cooldown period and health check grace period.

Answer

Enable connection draining on the ALB target group and increase the deregistration delay.

Answer

Change the health check type to ELB and mark instances unhealthy before deployment.

Question 9

A company runs a critical microservices application on Amazon EKS with multiple services. They use an ingress controller (ALB Ingress Controller) to route traffic to services. They notice that when a pod fails, new requests are still sent to the failed pod for a few seconds, causing errors. The health check interval is set to 5 seconds. They want to minimize the time during which failed pods receive traffic. They also need to ensure that during rolling updates, traffic is not sent to pods that are terminating. Which solution should they implement?

Accepted Answer

Configure readiness probes on the pods and set the ALB ingress controller to use the readiness probe endpoint.. Readiness probes detect when a pod is not ready to serve traffic and remove it from the service endpoints quickly. The ALB ingress controller respects readiness probes. Option A is incorrect because liveness probes restart pods but do not remove them from service immediately. Option B is incorrect because pod anti-affinity affects scheduling, not traffic routing. Option C is incorrect because decreasing the health check interval on the ALB target group to 2 seconds may reduce detection time but does not address the issue of traffic being sent to terminating pods during rolling updates as effectively as readiness probes.

Answer

Define liveness probes for all pods with a low failure threshold.

Answer

Use pod anti-affinity to spread pods across nodes.

Answer

Decrease the health check interval on the ALB target group to 2 seconds.

Question 10

A company runs a web application on EC2 instances behind an Application Load Balancer (ALB). The application stores session state in an RDS MySQL database. During a recent spike in traffic, the database CPU utilization reached 100%, causing slow responses. To improve resilience, what should a DevOps engineer do?

Accepted Answer

Migrate session state to Amazon ElastiCache for Redis with replication.. Amazon ElastiCache for Redis provides a low-latency, in-memory session store that offloads the database, improving resilience under load. Option A (scaling RDS) only addresses database capacity, not offloading session state. Option B (ElastiCache Memcached) is possible but Redis is more commonly used for session state with persistence and replication. Option D (Auto Scaling groups) does not address the database bottleneck.

Answer

Migrate session state to Amazon ElastiCache for Memcached.

Answer

Increase the RDS instance size and enable Multi-AZ deployment.

Answer

Configure Auto Scaling groups for the EC2 instances based on CPU utilization.

Question 11

A DevOps team is designing a highly available multi-tier application on AWS. The application runs on EC2 instances in an Auto Scaling group across two Availability Zones. The team uses an Application Load Balancer (ALB) to distribute traffic. The application requires the ALB to be accessible via a single, static IP address for whitelisting by third-party partners. What is the most resilient solution?

Accepted Answer

Use a Network Load Balancer (NLB) with an Elastic IP per Availability Zone and front it with AWS Global Accelerator.. It combines a Network Load Balancer (NLB) with Elastic IPs per Availability Zone for static IP addresses, and AWS Global Accelerator provides static anycast IP addresses, improved performance via the AWS global network, and automatic failover across AZs, ensuring high resilience. Option A is incorrect because Route 53 weighted routing adds DNS-level failover latency and does not provide a single static IP. Option C is incorrect because attaching Elastic IPs to subnets is not a valid configuration; NLBs use Elastic IPs per AZ but need Global Accelerator for global static IPs and better resilience. Option D is incorrect because an ALB does not support Elastic IPs; its IPs can change, so Global Accelerator is needed for static IPs but the NLB combination is more resilient due to native static IPs.

Answer

Use a Network Load Balancer (NLB) with a static IP address and Route 53 weighted routing to multiple NLBs.

Answer

Use a Network Load Balancer (NLB) with Elastic IP addresses attached to each subnet in each AZ.

Answer

Use an Application Load Balancer (ALB) with AWS Global Accelerator.

Question 12

A company has a microservices architecture running on Amazon ECS with Fargate launch type. Each service is deployed in multiple Availability Zones. The services communicate via REST APIs. Recently, a downstream service experienced a partial outage, causing upstream services to time out and leading to cascading failures. The team wants to improve resilience against such failures. Which combination of actions should the DevOps engineer take? (Choose TWO.)

Accepted Answer

Implement circuit breaker patterns in the service clients.. Options B and D are correct. Implementing circuit breaker patterns in service clients (e.g., using AWS App Mesh or resilience libraries) helps prevent cascading failures by failing fast when a downstream service is unhealthy, allowing upstream services to recover quickly. Adopting an asynchronous communication pattern using Amazon SQS or Amazon EventBridge decouples services, so upstream services can continue processing requests even if a downstream service is temporarily unavailable, by queuing messages for later consumption. Option A (increasing timeouts) can exacerbate the problem by holding connections longer and consuming resources. Option C (removing retries) is too aggressive and may cause data loss; controlled retries with exponential backoff are better. Option E (Auto Scaling) addresses capacity but does not directly handle partial outages or prevent cascading failures.

Answer

Increase the HTTP timeout values for all service-to-service calls.

Answer

Remove all retry logic from service calls.

Answer

Configure Auto Scaling for all services based on request count.

Question 13

A DevOps engineer is designing a disaster recovery (DR) strategy for a stateless web application running on EC2 instances with an Application Load Balancer. The application stores data in Amazon S3 and uses a DynamoDB table for session data. The primary region is us-east-1 and the DR region is us-west-2. The RTO is 15 minutes and RPO is 1 minute. Which strategy is most cost-effective and meets the requirements?

Accepted Answer

Use a warm standby with a minimal environment in the DR region, using DynamoDB Global Tables and S3 CRR, with Auto Scaling to scale up on failover.. A warm standby with a minimal environment (e.g., a single small EC2 instance) in the DR region is cost-effective while still meeting RTO and RPO. DynamoDB Global Tables provide active-active replication with sub-second RPO, and S3 CRR replicates objects within minutes (RPO < 1 minute). On failover, Auto Scaling can quickly scale up the fleet to handle full traffic, achieving RTO of 15 minutes. Option B (warm standby with fully functional scaled-down environment) is more costly because it maintains a complete set of resources (e.g., ALB, Auto Scaling group) even if scaled down. Option C (multi-site active-active) is unnecessarily complex and expensive for a stateless app that doesn't require active-active. Option D (pilot light) would require provisioning resources on failure, which likely exceeds the 15-minute RTO.

Answer

Use a warm standby strategy with a scaled-down but fully functional environment in the DR region.

Answer

Use a multi-site active-active strategy, running the application in both regions with a Route 53 latency-based routing.

Answer

Use a pilot light strategy with CloudFormation templates to provision resources in the DR region on failure.

Question 14

A company runs a containerized application on Amazon ECS with Fargate. The application uses an Application Load Balancer (ALB) and stores data in Amazon Aurora Serverless v2. The application experiences intermittent timeouts during periods of rapid scaling. The DevOps engineer notices that the Aurora database's ACU utilization spikes to 100% during these events. What should the engineer do to improve resilience? (Choose THREE.)

Accepted Answer

Implement exponential backoff and jitter in application retry logic.. Exponential backoff and jitter in retry logic prevent thundering herd during scaling events, reducing load on the database. Option D is correct because configuring Aurora Auto Scaling with a higher maximum ACU allows the database to handle increased traffic bursts, preventing ACU saturation. Option E is correct because Amazon RDS Proxy manages database connections efficiently, reducing connection overhead and improving scalability during rapid scaling. Option A is incorrect because increasing Fargate task memory/CPU does not address the database bottleneck; the issue is database ACU saturation. Option C is incorrect because ElastiCache caches reads, but the issue is likely write-heavy scaling; caching does not alleviate write load.

Answer

Increase the Fargate task memory and CPU limits.

Answer

Add Amazon ElastiCache in front of the database for caching.

Question 15

A company uses AWS CloudFormation to deploy infrastructure. The DevOps team wants to ensure that if a stack update fails, the stack automatically rolls back to the previous known good state. The team also wants to receive notifications of the rollback. Which combination of steps should the team take? (Choose THREE.)

Accepted Answer

Set the 'Rollback on failure' option to 'Yes' in the CloudFormation stack properties.. Setting 'Rollback on failure' to 'Yes' in the CloudFormation stack properties ensures automatic rollback to the last known good state if the update fails. Option C is correct because configuring an SNS topic as a notification target allows the stack to send notifications (e.g., email) about rollback events. Option B is incorrect because termination protection only prevents accidental deletion of the stack; it does not affect rollback behavior or notifications. Option D is incorrect because CloudWatch Logs log groups are used for storing logs, not for notifications or rollback. Option E is incorrect because drift detection identifies manual changes to resources but does not provide rollback or notifications.

Answer

Enable termination protection on the CloudFormation stack.

Answer

Create a CloudWatch Logs log group and subscribe to stack events.

Answer

Enable drift detection on the CloudFormation stack.