DOP-C02 Resilient Cloud Solutions Practice Test 16 — 15 Questions

Question 1

A company is designing a resilient architecture for a critical application. Which TWO strategies improve resilience?

Accepted Answer

Deploy resources across multiple Availability Zones. Multi-AZ deployments and health checks with auto-remediation improve resilience by handling failures automatically.

Answer

Use a single large instance instead of multiple smaller ones

Answer

Disable automated backups to reduce latency

Answer

Deploy resources in a single Availability Zone

Question 2

A company runs a microservices architecture on Amazon ECS. They want to ensure that if a service fails, it does not cascade to other services. Which TWO design patterns should they implement?

Accepted Answer

Circuit breaker pattern. The circuit breaker pattern (C) is correct because it wraps calls to a failing downstream microservice and, after a threshold of failures, trips open to fail fast instead of repeatedly invoking the unhealthy service, preventing a localized failure from cascading through the call chain. The bulkhead pattern (E) is correct because it isolates resources such as thread pools, connection pools, or ECS tasks per service or dependency, so exhaustion or failure in one component cannot consume shared capacity and take down other services. Together these patterns directly address fault isolation and cascade prevention in a microservices architecture on Amazon ECS. The cache-aside pattern (A) only improves read performance and reduces backend load by populating a cache on demand; it does not stop failure propagation. The Saga pattern (B) manages distributed transaction consistency across services via compensating actions, which is about data integrity rather than preventing cascading failures. The throttling pattern (D) limits request rates to protect a service from overload, but it is a rate-control mechanism and not the primary isolation pattern for stopping cross-service failure cascades.

Answer

Cache-aside pattern

Answer

Saga pattern

Answer

Throttling pattern

Question 3

A company wants to protect its application from DDoS attacks. Which THREE AWS services should they use?

Accepted Answer

AWS WAF. AWS Shield Advanced, WAF, and CloudFront provide layered DDoS protection.

Answer

Amazon Inspector

Answer

Amazon GuardDuty

Question 4

A company is deploying a critical application on Amazon EC2 instances behind an Application Load Balancer (ALB) across multiple Availability Zones. The application must be resilient to the failure of an entire Availability Zone. Which design should the company implement?

Accepted Answer

Launch EC2 instances in at least two Availability Zones and place them behind an Application Load Balancer with cross-zone load balancing enabled.. Deploying EC2 instances across at least two Availability Zones (AZs) behind an Application Load Balancer (ALB) with cross-zone load balancing enabled ensures that if an entire AZ fails, the ALB can route traffic to healthy instances in the remaining AZs. Cross-zone load balancing allows the ALB to distribute incoming requests evenly across all registered instances in all enabled AZs, which improves fault tolerance and resource utilization. This design meets the requirement for resilience to an AZ failure by eliminating a single point of failure at the AZ level.

Answer

Use one EC2 instance in a single Availability Zone behind a Network Load Balancer.

Answer

Launch EC2 instances in one Availability Zone and use an Application Load Balancer to distribute traffic.

Answer

Deploy EC2 instances in two Availability Zones but use a single Application Load Balancer in one AZ.

Question 5

A DevOps team is designing a disaster recovery solution for an Amazon RDS for MySQL database. The primary database is in us-east-1, and the recovery point objective (RPO) is 5 minutes, recovery time objective (RTO) is 1 hour. Which solution meets these requirements?

Accepted Answer

Create a cross-Region read replica in the secondary Region.. A cross-Region read replica in the secondary Region meets the RPO of 5 minutes because replication from the primary RDS instance to the read replica is asynchronous but typically completes within seconds to a few minutes, well under the 5-minute threshold. In a disaster, promoting the read replica to a standalone instance can be done manually or automated, and the RTO of 1 hour is achievable because promotion takes only a few minutes, leaving ample time for DNS and application failover. This solution provides a continuous replication stream without manual intervention, unlike snapshot-based approaches.

Answer

Enable Multi-AZ deployment for high availability.

Answer

Take manual snapshots and copy them to the secondary Region daily.

Answer

Configure automated backups with a retention period of 35 days.

Question 6

A company runs a stateless web application on Amazon ECS with Fargate launch type. The application experiences intermittent traffic spikes. The company wants to ensure that the application can scale automatically and remain resilient to underlying infrastructure failures. Which combination of actions should the DevOps engineer take?

Accepted Answer

Configure an Application Auto Scaling target tracking policy based on memory utilization and enable Amazon ECS service auto-recovery.. It combines Application Auto Scaling target tracking based on memory utilization, which is a relevant metric for a stateless web application to handle traffic spikes, with Amazon ECS service auto-recovery, which automatically replaces unhealthy tasks to ensure resilience against underlying infrastructure failures. This approach provides both automatic scaling and fault tolerance without manual intervention.

Answer

Configure a scheduled scaling policy for the Amazon ECS service to add tasks during known peak hours.

Answer

Launch tasks in a single Availability Zone and use an Application Auto Scaling target tracking policy based on CPU utilization.

Answer

Configure a step scaling policy for the Amazon ECS service and increase the task memory size.

Question 7

A company has a production environment that uses Amazon Route 53 for DNS and an Application Load Balancer (ALB) to distribute traffic to EC2 instances. The company wants to implement a disaster recovery plan that automatically fails over to a secondary region in case the primary region becomes unavailable. Which configuration should be used?

Accepted Answer

Use Route 53 failover routing policy with primary and secondary records and health checks.. Route 53 failover routing is purpose-built for active-passive DR: you designate a PRIMARY record and a SECONDARY record, attach a health check to the primary, and Route 53 automatically returns the secondary record's value when the primary health check fails. This gives deterministic, automatic regional failover without manual DNS changes. The other policies distribute traffic but do not implement a primary/secondary failover decision.

Answer

Use Route 53 weighted routing policy with equal weights for both regions.

Answer

Use Route 53 geolocation routing policy to route users based on their location.

Answer

Use Route 53 latency routing policy to route to the region with lowest latency.

Question 8

A company runs a critical microservice on Amazon ECS with AWS Fargate. The service must be highly available across multiple Availability Zones. The DevOps engineer configured the service with a desired count of 4 tasks spread across 2 Availability Zones. During a deployment, a new task fails to start due to a missing environment variable. The deployment fails, but the old tasks continue to run. What is the most likely cause of the deployment failure and how can the engineer ensure future deployments are resilient?

Accepted Answer

The deployment failed because the ECS service did not have the deployment circuit breaker enabled. Enable the circuit breaker with rollback.. The deployment failed because the new task could not start due to a missing environment variable, and the ECS service did not have the deployment circuit breaker enabled. Without the circuit breaker, ECS continues to attempt the deployment indefinitely or until a timeout, but it does not automatically roll back to the previous stable task set. Enabling the deployment circuit breaker with rollback ensures that if a specified number of tasks fail to start (e.g., due to health checks or runtime errors), ECS automatically rolls back to the last successful deployment, maintaining service availability.

Answer

The deployment failed because the ECS service was using the rolling update deployment controller. Change to blue/green deployment.

Answer

The deployment failed because the desired count was too low. Increase the desired count to 6.

Answer

The deployment failed because the health check grace period was too short. Increase the grace period.

Question 9

A company uses Amazon DynamoDB as the database for a mobile application. The application requires single-digit millisecond read and write latency and must be resilient to the failure of an entire AWS Region. Which DynamoDB feature should the company use?

Accepted Answer

DynamoDB global tables. DynamoDB global tables provide multi-Region, multi-active replication, ensuring the application can withstand an entire AWS Region failure while maintaining single-digit millisecond read and write latency in each Region. This is achieved through DynamoDB Streams and a last-writer-wins conflict resolution mechanism, making it the correct choice for cross-Region resilience.

Answer

DynamoDB point-in-time recovery (PITR)

Answer

DynamoDB Accelerator (DAX)

Answer

DynamoDB on-demand capacity mode

Question 10

A company runs a web application on AWS that uses Amazon SQS to decouple the frontend from the backend processing. The application experiences sudden spikes in traffic, causing the SQS queue to accumulate a large number of messages. The backend workers are unable to process messages fast enough, leading to increased latency. What solution can the company implement to improve the resilience and scalability of the backend?

Accepted Answer

Configure an Auto Scaling group for the backend workers with a scaling policy based on the SQS queue depth.. Configuring an Auto Scaling group for the backend workers with a scaling policy based on the SQS queue depth (ApproximateNumberOfMessagesVisible) directly addresses the sudden traffic spikes. This approach dynamically adds more worker instances when the queue depth increases, improving processing throughput and reducing latency. It ensures the backend scales in response to demand, enhancing both resilience and scalability.

Answer

Reduce the receive message wait time (long polling) to poll the queue more frequently.

Answer

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

Answer

Use an SQS FIFO queue instead of a standard queue to ensure ordered processing.

Question 11

A company is implementing a disaster recovery strategy for its Amazon Aurora MySQL database. The primary database is in us-west-2. The company requires an RPO of less than 1 minute and an RTO of less than 5 minutes. Which solution meets these requirements?

Accepted Answer

Use Amazon Aurora Global Database with a secondary Region cluster.. Amazon Aurora Global Database is designed for low-latency cross-Region replication with a typical RPO of 1 second and RTO of 1 minute or less, meeting the <1 minute RPO and <5 minute RTO requirements. It uses a dedicated storage-level replication channel that keeps the secondary cluster fully synchronized without impacting primary performance, and failover involves promoting the secondary cluster to primary in under a minute.

Answer

Create a cross-Region read replica in the secondary Region and promote it during failover.

Answer

Use automated backups and restore to a new DB instance in the secondary Region.

Answer

Take manual snapshots of the DB instance and copy them to the secondary Region every hour.

Question 12

A company is designing a highly available architecture for a web application that uses Amazon EC2 instances. The application must be resilient to the failure of a single instance and a single Availability Zone. Which TWO actions should the company take? (Choose TWO.)

Accepted Answer

Use an Auto Scaling group with a minimum of two instances spread across two Availability Zones.. An Auto Scaling group with a minimum of two instances spread across two Availability Zones ensures that if one instance or one entire AZ fails, the remaining instance(s) in the other AZ can continue serving traffic, and Auto Scaling will automatically launch a replacement instance in the healthy AZ to restore the desired count. Option B is correct because distributing EC2 instances across at least two Availability Zones is the fundamental requirement for AZ-level resilience, as it eliminates a single point of failure at the AZ boundary.

Answer

Place all EC2 instances in a single Availability Zone and use a Network Load Balancer.

Answer

Use a single Application Load Balancer in one Availability Zone.

Answer

Use a single large EC2 instance in one Availability Zone.

Question 13

A company is using AWS CloudFormation to deploy a critical application stack. The company wants to ensure that the stack can be recovered quickly in case of a failure. Which THREE strategies should the company implement? (Choose THREE.)

Accepted Answer

Use StackSets to deploy the stack across multiple Regions.. AWS CloudFormation StackSets allow you to deploy stacks across multiple AWS Regions and accounts from a single template, enabling multi-Region disaster recovery. By deploying the critical application stack in multiple Regions, you can quickly fail over to a secondary Region if the primary fails, meeting the requirement for rapid recovery.

Answer

Disable rollback on stack creation failure to preserve resources for debugging.

Answer

Define the entire application in a single CloudFormation template.

Question 14

A company is designing a disaster recovery plan for an Amazon S3 data lake. The data lake stores sensitive data that must be replicated to a secondary Region with an RPO of 15 minutes. Which THREE actions should the company take? (Choose THREE.)

Accepted Answer

Enable S3 Versioning on both the source and destination buckets.. Enabling S3 Versioning on both the source and destination buckets is a prerequisite for S3 Replication. Without versioning, replication cannot track object versions, which is essential for meeting the 15-minute RPO with consistency guarantees.

Answer

Configure S3 Event Notifications to trigger a Lambda function that copies objects to the secondary Region.

Answer

Enable S3 Transfer Acceleration on the source bucket.

Question 15

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 only allows the s3:PutObject action when the encryption condition is met, but it does not include an explicit Deny statement to block uploads that do not satisfy the condition. In IAM, an Allow statement with a condition does not automatically deny requests that fail the condition; it simply does not apply the Allow. If there is another policy (e.g., a bucket policy or an identity-based policy) that grants s3:PutObject without the encryption condition, or if the default S3 behavior permits unencrypted uploads (since S3 does not require encryption by default), then unencrypted uploads can still succeed. To enforce encryption, you must add a Deny statement with a condition like `StringNotEquals` on `s3:x-amz-server-side-encryption` to explicitly reject requests that lack the required encryption header.

Answer

The policy uses StringEquals instead of StringNotEquals.

Answer

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

Answer

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