DOP-C02 Resilient Cloud Solutions Practice Test 5 — 15 Questions

Question 1

A company runs a critical application on Amazon ECS with Fargate launch type. The application is deployed across multiple Availability Zones. The DevOps team needs to ensure that if an entire Availability Zone fails, the application continues to serve traffic without manual intervention. What should the team do?

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

Accepted Answer

Configure the ECS service to run tasks in at least two Availability Zones and enable the ECS service auto-recovery feature.. The ECS service's AZ rebalancing feature automatically redistributes tasks across Availability Zones when an imbalance is detected, such as after an AZ failure. By configuring the service to run tasks in at least two AZs and enabling this feature, the ECS service will automatically launch replacement tasks in the remaining healthy AZs to maintain the desired count, ensuring continued traffic serving without manual intervention.

Answer

Use an Amazon ECS service auto-scaling policy to automatically replace tasks in the failed AZ.

Answer

Configure the ALB to enable cross-zone load balancing and enable the ECS service's AZ rebalancing feature.

Answer

Set the ECS service's minimum healthy percent to 100 and maximum percent to 200.

Question 2

A company is running a stateful web application on Amazon EC2 instances. The application stores session data locally on the instance. The company wants to make the application stateless and improve resilience. The DevOps team decides to use Amazon ElastiCache for Redis to store session data. What additional step should the team take to ensure that the session data is highly available?

Accepted Answer

Enable ElastiCache for Redis cluster mode with automatic failover across multiple Availability Zones.. Enabling ElastiCache for Redis cluster mode with automatic failover across multiple Availability Zones ensures that if the primary node fails, a read replica in another AZ is promoted, providing high availability for session data. Option A is wrong because Multi-AZ for standard Redis provides automatic failover but does not include the partition tolerance and scalability benefits of cluster mode; for session data that needs high availability and scalability, cluster mode is recommended. Option B is wrong because a single node offers no redundancy; relying on application reconnection does not guarantee data availability during node failure. Option D is wrong because backing up to S3 provides durability but not automatic failover; during a failure, you would need to restore from backup, which is not automatic and incurs downtime.

Answer

Deploy ElastiCache for Redis in a Multi-AZ configuration with automatic failover.

Answer

Use a single ElastiCache for Redis node and rely on the application to reconnect if the node fails.

Answer

Configure ElastiCache for Redis to back up session data to Amazon S3 every 5 minutes.

Question 3

A company has an Amazon S3 bucket that stores critical data. The company wants to protect the data from accidental deletion and ensure that even the root user cannot delete the bucket. Which S3 feature should the company enable?

Accepted Answer

S3 bucket policy that denies s3:DeleteBucket for all principals.. A bucket policy with an explicit Deny on s3:DeleteBucket for Principal '*' does apply to and block the root user for that resource-level action, since explicit denies in resource-based policies are enforced regardless of principal. This is the deliberate mechanism the exam_trap/common_trap_note fields describe as correct.

Answer

S3 bucket versioning with MFA delete.

Answer

S3 Object Lock with compliance retention mode.

Answer

S3 bucket versioning with lifecycle policy to expire noncurrent versions.

Question 4

A company's production database on Amazon RDS Multi-AZ DB instance experienced a failover. The application experienced a brief outage. How can the company reduce the failover time?

Accepted Answer

Use Amazon RDS Proxy. Amazon RDS Proxy sits between the application and the database, maintaining a warm connection pool and transparently redirecting connections to the new primary during a failover. This reduces the failover time perceived by the application because it eliminates the need for the application to re-establish connections and re-resolve DNS, cutting downtime from minutes to typically under a minute.

Answer

Switch to a Single-AZ deployment

Answer

Increase the DB instance size

Answer

Enable Enhanced Monitoring

Question 5

A company wants to design a disaster recovery solution for its primary AWS Region. The solution should have a Recovery Point Objective (RPO) of a few seconds and a Recovery Time Objective (RTO) of a few minutes. Which strategy meets these requirements?

Accepted Answer

Multi-Region active-active. Multi-Region active-active is the only strategy that can achieve an RPO of a few seconds and an RTO of a few minutes. In an active-active configuration, both Regions serve production traffic simultaneously, and data is continuously replicated (e.g., via DynamoDB global tables or Aurora global database) so that the standby Region is always current. Because the secondary Region is already running at full capacity, failover is nearly instantaneous, meeting the tight RTO. The continuous replication ensures that almost no data is lost, satisfying the RPO requirement.

Answer

Pilot light

Answer

Backup and restore

Answer

Warm standby

Question 6

A company's application on Amazon ECS experiences intermittent failures when the task attempts to access an S3 bucket. The task role has the correct S3 permissions. What is the most likely cause?

Accepted Answer

The S3 bucket policy explicitly denies access from the task's VPC. The most likely cause is that the S3 bucket policy explicitly denies access from the task's VPC. Even if the task role has correct S3 permissions, an explicit deny in the bucket policy overrides any allow. This can happen if the bucket policy includes a condition that denies requests from certain VPCs or VPC endpoints.

Answer

The task is using the wrong IAM role

Answer

The S3 bucket is in a different region

Answer

The S3 bucket has public access blocked

Question 7

A company is using Amazon S3 to store critical data. The company requires that all versions of objects be retained, including deleted objects, to meet compliance requirements. Which S3 feature should be enabled?

Accepted Answer

S3 Versioning. S3 Versioning keeps all versions of objects, including deleted ones (marked with delete markers). Option B is wrong because S3 Object Lock prevents deletion or modification of objects but does not itself retain all versions; versioning must also be enabled. Option C is wrong because S3 Lifecycle policies automate transitioning or expiring objects, not retaining all versions. Option D is wrong because MFA Delete adds an extra layer of security to versioning operations but does not retain all versions.

Answer

S3 Object Lock

Answer

S3 Lifecycle policies

Answer

MFA Delete

Question 8

Refer to the exhibit. A DevOps engineer applies the IAM policy shown to an S3 bucket to enforce server-side encryption. However, users report that some uploads succeed without encryption. What is the most likely reason?

Accepted Answer

The policy only allows the action but does not deny actions that do not meet the condition.. The IAM policy shown only allows the s3:PutObject action when the encryption condition is met, but it does not include a Deny statement to explicitly block uploads that do not satisfy the condition. In AWS IAM, an Allow statement alone does not prevent actions that fail the condition; it simply grants permission when the condition is true. Without a corresponding Deny, users with other permissions (e.g., from a broader policy) can still upload objects without encryption, as the Allow does not override other effective allows.

Answer

The resource ARN is incorrect; it should be the bucket ARN.

Answer

The action should be s3:PutEncryptedObject instead of s3:PutObject.

Answer

The policy uses StringEquals instead of StringNotEquals.

Question 9

A company runs a critical application on Amazon ECS with Fargate launch type. The application is deployed across multiple Availability Zones. The DevOps team needs to ensure that if an entire Availability Zone fails, the application continues to serve traffic without manual intervention. What should the team do?

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

Accepted Answer

The Auto Scaling group was configured to span only two Availability Zones, and the failed AZ contained a majority of the running instances. If the Auto Scaling group is configured to span only two Availability Zones, the failure of one AZ would result in a disproportionate loss of capacity. Since the failed AZ contained a majority of the running instances, the remaining instances in the surviving AZ would be overloaded, causing significant performance degradation. The application remained available because the surviving instances and the Multi-AZ RDS instance continued to operate, but the reduced compute capacity led to degraded performance.

Answer

The Route 53 health checks failed and directed traffic to another Region, increasing latency

Answer

The RDS DB instance failed over to a read replica in a different Region

Answer

The EBS volumes in the failed AZ were not available, causing data loss

Question 10

A company's application runs on Amazon ECS with Fargate launch type. The application must be resilient to an Availability Zone failure. Which configuration should be used?

Accepted Answer

Create an ECS service with tasks distributed across multiple Availability Zones using a spread placement strategy. ECS services using the Fargate launch type can distribute tasks across multiple Availability Zones (AZs) by defining a spread placement strategy with the 'availabilityZone' dimension. This ensures that if one AZ fails, the tasks in the other AZs continue to serve traffic, providing resilience to an AZ failure. The spread strategy explicitly instructs ECS to place tasks evenly across AZs, which is essential for high availability.

Answer

Use an ECS cluster with a cluster placement strategy that prefers the same Availability Zone

Answer

Define multiple task definitions, one for each Availability Zone

Answer

Use an ECS service with a single task in one Availability Zone and rely on auto-scaling

Question 11

A company is designing a disaster recovery plan for an application running on AWS. The plan must meet an RTO of 1 hour and an RPO of 15 minutes. Which TWO strategies can achieve these objectives? (Select TWO.)

Accepted Answer

Warm standby in a different AWS Region with database replication. (Warm standby) is correct because it maintains a scaled-down but fully functional copy of the production environment in a different AWS Region, with database replication (e.g., Amazon RDS cross-Region read replicas or Aurora Global Database) ensuring an RPO of 15 minutes or less. The standby infrastructure can be scaled up within the 1-hour RTO, as it is already running and configured.

Answer

Backup and restore using daily snapshots to a different Region

Answer

Cold standby in a different Region with infrastructure deployed on demand

Answer

Multi-AZ deployment in the same Region

Question 12

A company runs a critical e-commerce application on Amazon EC2 instances behind an Application Load Balancer (ALB) with Auto Scaling. The application must be resilient to an Availability Zone (AZ) failure. What is the MOST resilient configuration?

Accepted Answer

Configure the Auto Scaling group to span at least three AZs and set the ALB to route traffic to all AZs.. Spanning the Auto Scaling group across at least three Availability Zones (AZs) and routing traffic from the ALB to all AZs ensures that if one AZ fails, the remaining AZs can handle the load without interruption. This configuration leverages the ALB's native cross-zone load balancing and Auto Scaling's ability to maintain desired capacity across multiple AZs, providing fault isolation and high availability for the critical e-commerce application.

Answer

Configure the Auto Scaling group to launch instances in a single AZ with a larger instance type.

Answer

Deploy a single large EC2 instance in one AZ and use an Elastic IP for failover.

Answer

Use a Network Load Balancer instead of an ALB and deploy instances in two AZs.

Question 13

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 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 via ECS and CodeDeploy provisions a new green task set alongside the still-serving blue tasks and registers it with a separate target group. Traffic is shifted by CodeDeploy in controlled percentage steps while ordinary CloudWatch alarms (not 'target tracking' alarms, which is a distinct autoscaling concept) monitor metrics like error rate or latency during the deployment; if any alarm breaches its threshold, CodeDeploy automatically rolls back to the blue task set. This architecture provides automated, reversible traffic shifting rather than a manual switch, which is the key operational requirement for safe continuous delivery.

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 financial services company runs a critical application on Amazon ECS with Fargate launch type. The application has strict availability requirements and must survive an Availability Zone failure. The ECS service is configured with a desired count of 4 tasks, spread across two Availability Zones using a spread strategy. The service is fronted by an Application Load Balancer. During a recent AZ outage, one AZ became completely unavailable, but the application continued to serve traffic. However, after the AZ recovered, the ECS service did not automatically place new tasks in the recovered AZ to restore the desired count. The service remains with only 2 tasks in the remaining AZ. What is the most likely cause and solution?

Accepted Answer

The ECS service does not automatically replace tasks in a recovered AZ because the spread strategy is static. Manually update the service (e.g., force new deployment) to trigger rebalancing.. The ECS service uses a spread strategy, which maintains balance across AZs. When an AZ is unhealthy, ECS does not place tasks there. After recovery, the service may not automatically rebalance because the spread strategy is not proactive; it only ensures placement of new tasks. To force rebalancing, one can update the service (e.g., change desired count, then change back).

Answer

The Application Load Balancer is not health-checking the recovered AZ. Configure cross-zone load balancing.

Answer

The ECS service uses a spread strategy that does not automatically rebalance after an AZ recovers. Update the service to use a 'rebalance' strategy.

Answer

The ECS service is configured with a minimum healthy percent of 50%, which prevents replacement. Lower the minimum healthy percent to 0%.