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

Question 1

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. Option B is correct because 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 2

A company is designing a serverless application using AWS Lambda, Amazon API Gateway, and Amazon DynamoDB. The application must tolerate a Regional failure. Which design provides the most resilience?

Accepted Answer

Use DynamoDB global tables with Lambda functions deployed in multiple Regions and Route 53 multi-Region routing. Option C is correct because DynamoDB global tables provide multi-Region, fully replicated tables with automatic conflict resolution, ensuring data availability during a Regional outage. Deploying Lambda functions in multiple Regions with Route 53 multi-Region routing (using health checks and latency-based or weighted routing) allows traffic to fail over to a healthy Region, making the entire serverless stack resilient to a Regional failure.

Answer

Use Lambda@Edge to run functions at AWS edge locations

Answer

Use DynamoDB auto-scaling and run Lambda in a single Region

Answer

Use DynamoDB Accelerator (DAX) to cache data across Regions

Question 3

A company runs a stateful web application on EC2 instances in an Auto Scaling group. The application uses an Application Load Balancer (ALB) and an Amazon ElastiCache Redis cluster. Users report that after a scaling event, they are logged out and lose session data. What is the most likely cause?

Accepted Answer

The ElastiCache cluster is not configured for Multi-AZ and a node failure caused all sessions to be lost. Option D is correct because the scenario describes a stateful web application that relies on ElastiCache Redis for session storage. If the ElastiCache cluster is not configured for Multi-AZ, a node failure can cause all cached session data to be lost, logging users out. This is the most likely cause of session loss after a scaling event, as scaling events do not directly affect ElastiCache data persistence.

Answer

The ALB health check interval is too short, causing healthy instances to be marked unhealthy

Answer

The ElastiCache cluster is configured with in-transit encryption, causing session tokens to be invalidated

Answer

The Auto Scaling group is using a termination policy that terminates the oldest instance first, which holds active sessions

Question 4

A company uses Amazon Route 53 to route traffic to an Application Load Balancer. They want to improve availability by routing traffic to multiple ALBs in different AWS Regions. Which routing policy should they use?

Accepted Answer

Latency-based routing policy. Latency-based routing policy is correct because it directs traffic to the AWS Region that provides the lowest latency for the end user, improving availability and performance by distributing requests across multiple Application Load Balancers in different regions. This policy uses latency measurements between the user and each region to select the optimal endpoint, ensuring that if one region becomes unavailable, traffic is automatically routed to the next lowest-latency region.

Answer

Weighted routing policy

Answer

Geolocation routing policy

Answer

Simple routing policy

Question 5

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. Option A is correct because 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 6

A company runs a critical application on EC2 instances behind an Application Load Balancer. The application uses an Amazon RDS for PostgreSQL Multi-AZ DB instance. During a recent failover test, the application experienced a 5-minute downtime. The RDS failover completed within 30 seconds. What is the most likely cause of the prolonged downtime?

Accepted Answer

The application caches DNS resolutions, causing it to connect to the old writer endpoint. The most likely cause is that the application caches DNS resolutions, causing it to continue connecting to the old writer endpoint after failover. When an RDS Multi-AZ failover occurs, the DNS record for the writer endpoint is updated to point to the new primary instance, but the application's cached DNS entry still points to the old IP address. Since the old primary is now a standby and no longer accepts connections, the application experiences downtime until the DNS cache expires (typically 5–60 seconds) or the application refreshes the DNS resolution. The 5-minute downtime suggests the application uses a long DNS TTL or a custom caching layer that delays reconnection.

Answer

The RDS Multi-AZ failover took longer than expected due to a large transaction log

Answer

The Application Load Balancer health checks marked all instances as unhealthy during the failover

Answer

The application was using read replicas for writes, which failed during failover

Question 7

A company is designing a highly available architecture for a web application using AWS. Which TWO of the following design principles should be applied? (Select TWO.)

Accepted Answer

Deploy resources across multiple Availability Zones. Correct answers: B and D. B spreads resources across AZs for fault tolerance. D decouples components to prevent cascading failures. A is wrong because single Region is not resilient. C is wrong because tightly coupled components reduce availability.

Answer

Run all resources in a single Availability Zone to reduce complexity

Answer

Store session data on EC2 instances to improve performance

Answer

Use tightly coupled components to reduce latency

Question 8

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. Option B (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 9

A company is migrating a monolithic application to a microservices architecture on AWS. To improve resilience, which THREE design patterns should be implemented? (Select THREE.)

Accepted Answer

Retry with exponential backoff for transient failures. Option C is correct because implementing retry with exponential backoff allows services to handle transient failures (e.g., network timeouts, throttling) by automatically retrying operations after increasing delays, reducing load on recovering systems. This pattern is essential for microservices on AWS, where services like DynamoDB or Lambda may throttle requests, and exponential backoff (e.g., using jitter as per AWS SDK defaults) prevents cascading failures.

Answer

Synchronous communication between services to ensure consistency

Answer

Single shared database to maintain data consistency

Question 10

A company runs a critical web application on EC2 instances in an Auto Scaling group. The application uses an Application Load Balancer (ALB) with health checks pointing to /health. Recently, the application experienced intermittent failures where the ALB would mark instances as unhealthy and route traffic away, causing a reduction in capacity. The development team noticed that the /health endpoint occasionally returns HTTP 503 when the application is under heavy load, but the application can recover quickly. The team wants to avoid unnecessary instance replacements while ensuring availability. Which solution should the DevOps engineer implement?

Accepted Answer

Increase the health check interval and increase the unhealthy threshold. Option B is correct because increasing the health check interval and unhealthy threshold reduces sensitivity to transient errors, avoiding unnecessary instance replacements. Option A is wrong because decreasing the interval makes the health check more sensitive, worsening the issue. Option C is wrong because reducing the unhealthy threshold makes it easier to mark instances unhealthy. Option D is wrong because custom actions are not necessary; the health check configuration can be tuned.

Answer

Implement a custom health check using Lambda that ignores 503 responses

Answer

Decrease the unhealthy threshold to mark instances unhealthy faster

Answer

Decrease the health check interval and decrease the healthy threshold

Question 11

A company has deployed a multi-tier application on AWS. The web tier uses an Auto Scaling group of EC2 instances behind an Application Load Balancer. The application tier uses another Auto Scaling group of EC2 instances that process messages from an Amazon SQS queue. The database tier uses Amazon RDS Multi-AZ. Recently, the application experienced a complete outage when the SQS queue became overwhelmed with messages due to a sudden spike in traffic. The application tier could not process messages fast enough, causing the queue to grow indefinitely and eventually exceed the visibility timeout, leading to message loss and degraded performance. The DevOps engineer needs to improve the resilience of the architecture to handle traffic spikes without losing messages. Which solution should be implemented?

Accepted Answer

Configure a dead-letter queue for unprocessed messages and implement Auto Scaling based on SQS queue depth. Option C is correct because a dead-letter queue captures messages that cannot be processed after a number of attempts, preventing loss. Combined with Auto Scaling based on queue depth, it ensures the application tier scales to handle spikes. Option A is wrong because increasing visibility timeout only delays re-processing, it does not prevent message loss. Option B is wrong because limiting queue size causes rejection of messages. Option D is wrong because SQS FIFO does not improve resilience against spikes and may reduce throughput.

Answer

Limit the maximum message size and set a queue size limit to prevent overflow

Answer

Replace the standard SQS queue with a FIFO SQS queue to ensure exactly-once processing

Answer

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

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.. Distributing instances across three AZs ensures that if one AZ fails, the remaining AZs can handle the load. This provides high availability and resilience.

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

A company uses AWS Lambda with Amazon DynamoDB to process orders. During peak hours, the Lambda function sometimes fails with throttling errors from DynamoDB. The system must be resilient and cost-effective. What should a DevOps engineer do?

Accepted Answer

Configure DynamoDB auto scaling and implement a dead-letter queue in Lambda to retry failed events.. Configuring DynamoDB auto scaling allows the table to handle increased throughput during peaks, reducing throttling. Adding a dead-letter queue and retries helps manage failed events without losing data.

Answer

Use Amazon SQS to buffer the requests and have Lambda pull from the queue with a reserved concurrency limit.

Answer

Increase the DynamoDB provisioned read and write capacity units to a high fixed value.

Answer

Provision DynamoDB Accelerator (DAX) to cache reads and reduce throttling.

Question 14

A DevOps team is designing a disaster recovery plan for an RDS MySQL database. The database must be recoverable with minimal data loss in case of a regional failure. Which solution provides the LOWEST Recovery Point Objective (RPO)?

Accepted Answer

Configure a Cross-Region Read Replica.. Cross-Region Read Replicas provide asynchronous replication with a typical RPO of seconds, offering minimal data loss.

Answer

Take daily automated snapshots and copy them to another Region.

Answer

Use a Multi-AZ deployment with synchronous standby.

Answer

Use RDS Proxy to cache database writes.

Question 15

A company runs a stateless web application on Amazon ECS with Fargate. The application must be highly available across multiple Availability Zones. What is the BEST way to achieve this?

Accepted Answer

Create an ECS service with tasks in multiple AZs and place an ALB in front.. Creating an ECS service with tasks distributed across multiple AZs and using an ALB to distribute traffic ensures high availability.

Answer

Use an Auto Scaling group of EC2 instances in a single AZ and run ECS tasks on them.

Answer

Deploy a CloudFront distribution with multiple origins in different AZs.

Answer

Deploy a single ECS service with tasks in one AZ and use an ALB.