DOP-C02 Resilient Cloud Solutions Practice Test 17 — 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 uses AWS Lambda functions to process events from an Amazon SQS queue. The Lambda function occasionally fails due to a transient downstream service error. The DevOps team wants to ensure that failed messages are not lost and can be retried later. The team also wants to reduce the number of invocations on the downstream service. Which configuration should the team use?

Accepted Answer

Configure a dead-letter queue (DLQ) on the SQS queue and set the Lambda function's reserved concurrency to 1.. Configuring a dead-letter queue (DLQ) on the SQS queue ensures that messages that exhaust their retries (due to Lambda failures) are preserved for later reprocessing, preventing data loss. Setting the Lambda function's reserved concurrency to 1 throttles the function to a single concurrent invocation, which naturally reduces the rate of downstream service calls and allows the SQS queue's visibility timeout and redrive policy to manage retry timing, thereby reducing pressure on the downstream service.

Answer

Configure an Amazon SNS topic as a Lambda destination for failure events and subscribe the SQS queue to it.

Answer

Configure a dead-letter queue (DLQ) on the Lambda function and set the function's maximum retry attempts to 2.

Answer

Configure the Lambda function to write failed messages to an Amazon DynamoDB table and set up a scheduled Lambda to retry.

Question 3

A company is building a serverless application using AWS Lambda, Amazon API Gateway, and Amazon DynamoDB. The application is expected to have unpredictable traffic patterns. The DevOps team needs to ensure that the application can handle sudden spikes in traffic without throttling. Which TWO actions should the team take? (Choose TWO.)

Accepted Answer

Use DynamoDB on-demand capacity mode for the table.. DynamoDB on-demand capacity mode automatically scales to handle unpredictable traffic spikes without requiring capacity planning or throttling. This mode charges per request and can accommodate sudden bursts of traffic up to the table's previous peak, making it ideal for serverless applications with variable workloads.

Answer

Configure DynamoDB auto scaling with a minimum capacity of 10 read/write capacity units.

Answer

Increase the Lambda function timeout to the maximum (15 minutes).

Answer

Set API Gateway throttling limits to a high value to prevent throttling.

Question 4

A company runs a stateful application on EC2 instances. The application stores session data locally. The instances are behind an ALB with sticky sessions enabled. A scaling event terminates an instance, causing loss of session data. How can the company prevent this while maintaining performance?

Accepted Answer

Use Amazon ElastiCache to store session data. Using ElastiCache for session storage externalizes session data, making it resilient to instance termination.

Answer

Use a dedicated EC2 instance for sessions

Answer

Disable sticky sessions

Answer

Increase the sticky session duration

Question 5

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 6

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 7

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 8

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 9

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 10

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 11

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 12

A company runs a stateless web application on EC2 instances behind an Application Load Balancer. To improve resilience, which configuration should be used for the EC2 instances?

Accepted Answer

Use multiple EC2 instances across two or more Availability Zones. D is correct because deploying multiple EC2 instances across two or more Availability Zones (AZs) ensures high availability and fault tolerance. If one AZ fails, the Application Load Balancer (ALB) automatically routes traffic to healthy instances in other AZs, maintaining service continuity. This aligns with the AWS Well-Architected Framework's resilience best practices for stateless applications.

Answer

Use one EC2 instance with a larger instance type

Answer

Use a single, large EC2 instance in one Availability Zone

Answer

Use multiple EC2 instances in one Availability Zone with health checks disabled

Question 13

A company wants to ensure that its application can recover from an Amazon S3 service disruption. The application reads and writes data to S3. Which strategy should the application implement to achieve resilience?

Accepted Answer

Implement application logic to fall back to an S3 bucket in a different Region if the primary bucket is unavailable. Implementing application logic to fall back to an S3 bucket in a different Region provides resilience against a regional S3 service disruption. S3 buckets are regional resources, so if one Region experiences an outage, the application can redirect reads and writes to a bucket in another Region. This approach requires the application to handle errors from the primary bucket and switch to the secondary bucket, ensuring continued availability without relying on automatic failover mechanisms that may not be instantaneous.

Answer

Store all data in a single S3 bucket with versioning enabled

Answer

Enable S3 Cross-Region Replication with automatic failover

Answer

Use S3 Transfer Acceleration to improve data transfer speed

Question 14

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 15

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