DOP-C02 Resilient Cloud Solutions Practice Test 4 — 15 Questions

Question 1

A company runs a stateless web application on a fleet of EC2 instances in an Auto Scaling group. The application stores session state in a shared ElastiCache Redis cluster. During traffic spikes, the application becomes slow. Monitoring shows that the Redis cluster has high CPU utilization. Which solution is MOST cost-effective and scalable?

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

Accepted Answer

Enable cluster mode on the ElastiCache Redis cluster and add more shards. Enabling cluster mode on ElastiCache Redis and adding more shards horizontally scales the cluster, distributing write and read operations across multiple nodes. This directly reduces CPU utilization on any single node and is more cost-effective than vertical scaling (upgrading to a larger node type) because it allows granular, pay-as-you-grow capacity. Cluster mode also supports automatic shard rebalancing and is ideal for stateless web applications with session state that can be partitioned by session key.

Answer

Upgrade the Redis instance to a larger node type to handle more operations

Answer

Add read replicas to offload read traffic from the primary node

Answer

Migrate session state to DynamoDB with DAX for caching

Question 2

A company runs a critical application on EC2 instances in an Auto Scaling group. The application uses an EBS volume attached to each instance for temporary data. The company needs to ensure that if an instance fails, the data is not lost, and the new instance can resume quickly. What should they do?

Accepted Answer

Use an EBS Multi-Attach volume attached to all instances in the Auto Scaling group. Using an EBS Multi-Attach volume allows multiple instances in the same Availability Zone to attach the same volume concurrently, enabling shared access and quick recovery without data loss. Option A is incorrect because instance store volumes are ephemeral and data is lost on instance failure. Option B is incorrect because restoring from an EBS snapshot takes time and may not provide quick resumption. Option C is incorrect because Amazon EFS is a file storage service, not block storage, and may not be suitable for applications that require raw block devices.

Answer

Store temporary data on instance store volumes instead of EBS

Answer

Use an EBS snapshot and create a new volume from the snapshot for the new instance

Answer

Migrate to Amazon EFS and mount the same file system on all instances

Question 3

A company runs a web application on EC2 instances behind an Application Load Balancer. The application uses an Aurora MySQL database. Recently, the database experienced a failover, and the application started throwing connection errors. The DevOps engineer needs to make the application resilient to database failovers with minimal code changes. What should they do?

Accepted Answer

Configure the application to use the Aurora cluster endpoint for database connections. The Aurora cluster endpoint always points to the current primary instance (writer). After a failover, the cluster endpoint automatically updates to point to the new writer, so the application reconnects without any code changes. Option B is incorrect because the reader endpoint is for read-only queries and does not direct to the writer. Option C is incorrect because a cross-Region read replica is read-only and cannot become the writer automatically; it does not solve failover resilience. Option D is incorrect because RDS Proxy provides connection pooling and IAM authentication but does not change the underlying endpoint behavior; you would still need to use the cluster endpoint to ensure automatic failover routing.

Answer

Configure the application to use the Aurora reader endpoint for all queries

Answer

Create a cross-Region read replica and configure the application to retry on failure

Answer

Use Amazon RDS Proxy with IAM authentication to handle connection pooling

Question 4

A company runs a microservices application on Amazon ECS with Fargate. The services need to be resilient to AZ failures. Which TWO actions should the company take? (Choose two.)

Accepted Answer

Configure the ECS service to spread tasks across multiple Availability Zones. To ensure resilience to Availability Zone failures, the company should spread tasks across multiple AZs (Option A) so that if one AZ fails, the tasks in other AZs continue to serve traffic. Additionally, enabling Service Auto Scaling (Option B) helps maintain the desired task count across AZs by automatically replacing tasks in failed AZs. Option C is incorrect because a single Network Load Balancer can route traffic across all AZs; placing one per AZ is unnecessary and adds complexity. Option D is irrelevant since placement groups apply to EC2 instances, not Fargate tasks. Option E is the opposite of resilience—placing all tasks in one AZ creates a single point of failure.

Answer

Use a Network Load Balancer in each AZ for the service

Answer

Use a placement group to ensure tasks are launched on the same underlying hardware

Answer

Place all tasks in a single Availability Zone to minimize cross-AZ latency

Question 5

An IAM policy is attached to an S3 bucket to allow access from a specific VPC CIDR range. However, users from the VPC are receiving 'Access Denied' errors when trying to access objects in the bucket. What is the MOST likely reason?

Accepted Answer

The condition key 'aws:SourceIp' evaluates the public IP address, but the VPC uses private IP addresses. The 'aws:SourceIp' condition key evaluates the source IP address of the request as seen by AWS, which is always a public IP address. When requests originate from within a VPC (e.g., from an EC2 instance), the source IP seen by S3 is the public IP of the instance or its NAT device, not the VPC's private CIDR range. Since the policy specifies a private VPC CIDR range using 'aws:SourceIp', it never matches the public source IP, resulting in 'Access Denied' errors.

Answer

The users are assuming an IAM role that does not have permission to access S3

Answer

The policy should use 'aws:sourceVpce' instead of 'aws:SourceIp' to restrict access to a VPC endpoint

Answer

The bucket policy requires HTTPS and the requests are using HTTP

Question 6

A DevOps engineer runs the above command and sees that one target is unhealthy with a 503 error. The application is a web server running on port 80. The health check is configured to hit the root path '/'. Which action should the engineer take to resolve the issue?

Accepted Answer

Verify that the application on the unhealthy instance is configured to respond to '/' with a 200 status code. The health check is configured to hit the root path '/' and expects a 200 status code. A 503 error indicates the application on the unhealthy instance is not serving the correct response for that path. Verifying that the application responds with a 200 status code on '/' directly addresses the root cause of the health check failure.

Answer

Change the health check port to 443 and use HTTPS

Answer

Increase the health check interval and timeout settings

Answer

Check the security group rules for the target group to ensure port 80 is open

Question 7

A company runs a critical web application on EC2 instances behind an Application Load Balancer. To improve resilience, they want to automatically replace failed instances. Which AWS service should they use?

Accepted Answer

Auto Scaling group with health checks. Auto Scaling groups with health checks automatically replace unhealthy instances based on ELB health check integration. Option D is correct. Option A (EC2 Instance Recovery) recovers instances on the same host but does not replace them if the host fails. Option B (Systems Manager Automation) requires manual or scheduled automation, not automatic health-based replacement. Option C (CloudFormation Stack update) does not provide auto-replacement; it manages infrastructure updates.

Answer

EC2 Instance Recovery

Answer

AWS Systems Manager Automation

Answer

CloudFormation Stack update

Question 8

A company is designing a multi-region active-active architecture for a stateless web application using Route 53 latency-based routing. The application uses an RDS MySQL database. What should be done to ensure database resilience across regions?

Accepted Answer

Create cross-region read replicas and promote to master during failover. To create cross-region read replicas and promote to master during failover. Cross-region read replicas allow the database to be promoted to a primary instance in another region, enabling database resilience across regions for an active-active architecture. Option A (automated snapshots copied to secondary region) is not suitable because restoring from snapshots is a manual process that takes time and does not support active-active. Option B is incorrect because RDS does not support synchronous cross-region replication; it only offers asynchronous replication via read replicas. Option D (Multi-AZ) is a single-region high-availability feature and does not address cross-region resilience.

Answer

Configure automated snapshots and copy them to the secondary region

Answer

Use RDS Cross-Region Synchronous Replication

Answer

Enable Multi-AZ deployment in each region

Question 9

A DevOps engineer needs to ensure that an application running on EC2 can automatically recover from an underlying hardware failure without manual intervention. Which AWS feature should be enabled?

Accepted Answer

Configure EC2 Auto Recovery with a CloudWatch alarm. EC2 Auto Recovery automatically recovers an instance when it becomes impaired due to underlying hardware failure, preserving its instance ID, private IP, and Elastic IP. Option A is incorrect because termination protection only prevents accidental deletion, not recovery. Option C is incorrect because an Auto Scaling group with a minimum size of 1 can replace a failed instance but launches a new instance rather than recovering the same one. Option D is incorrect because CloudWatch detailed monitoring provides more frequent metrics but does not trigger recovery actions.

Answer

Enable termination protection

Answer

Configure an Auto Scaling group with a minimum size of 1

Answer

Enable CloudWatch detailed monitoring

Question 10

A company is deploying a critical microservice on Amazon ECS with Fargate. They need to ensure that the service can tolerate an Availability Zone failure. What is the BEST approach?

Accepted Answer

Define the service to spread tasks across multiple Availability Zones. Amazon ECS with Fargate allows you to define a service with a 'spread across Availability Zones' strategy. By setting the service's placement strategy to spread tasks across multiple Availability Zones, the service automatically distributes tasks evenly across the specified AZs. If one AZ fails, the remaining tasks in other AZs continue to serve traffic, ensuring high availability. This is the most direct and effective method for tolerating an AZ failure in a Fargate-based deployment.

Answer

Use a cluster placement constraint to spread tasks across instances

Answer

Use EC2 launch type and spread tasks across instance types

Answer

Configure service auto scaling to add tasks when CPU is high

Question 11

A company runs an application on EC2 with a shared Elastic IP. The instance fails and an engineer manually attaches the Elastic IP to a standby instance. To automate this failover, which service should be used?

Accepted Answer

CloudWatch Events with a Lambda target. C is correct because CloudWatch Events (now Amazon EventBridge) can detect the EC2 instance state change (e.g., 'stopped' or 'failed') and trigger a Lambda function. The Lambda function can then programmatically disassociate the Elastic IP from the failed instance and reassociate it to a standby instance using the AWS SDK (e.g., ec2.disassociate_address and ec2.associate_address). This provides a fully automated, event-driven failover without manual intervention.

Answer

Use an Auto Scaling group with a lifecycle hook

Answer

AWS Elastic Beanstalk

Answer

Configure a second Elastic IP

Question 12

A company wants to protect its S3 bucket data from accidental deletion or overwrite. Which feature should be enabled?

Accepted Answer

Enable S3 Versioning. S3 Versioning is the primary feature that protects against accidental deletion and overwrite by preserving all versions of objects. When versioning is enabled, deleted objects are replaced with a delete marker and previous versions can be restored. MFA Delete (option D) is an additional security feature that requires multi-factor authentication for versioning operations, but versioning itself is the foundational protection. Option A (cross-region replication) is used for geographic redundancy and compliance, not for protecting against accidental deletions. Option B (bucket policy denying DeleteObject) would prevent deletions but does not protect against overwrites (PutObject) and can be overly restrictive; also, it may not allow legitimate deletions if not carefully scoped. Therefore, enabling S3 Versioning is the correct and most straightforward solution.

Answer

Enable cross-region replication

Answer

Apply a bucket policy that denies DeleteObject

Answer

Enable MFA Delete

Question 13

A company has a multi-region application with an RDS for MySQL database in us-east-1. They want to minimize downtime if the primary region fails. They set up a cross-region read replica in us-west-2. What additional step is needed for automated failover?

Accepted Answer

Use a custom automation to monitor the primary and promote the replica. B is correct because RDS cross-region read replicas do not support automatic failover; you must use custom automation (e.g., AWS Lambda, Amazon Route 53 health checks, or a custom script) to detect primary region failure and promote the read replica to a standalone instance. This promotion breaks the replication link and makes the replica a writable primary, enabling failover.

Answer

Create a second read replica in the secondary region

Answer

Configure automatic backup retention on the replica

Answer

Enable Multi-AZ on the read replica

Question 14

A company is designing a disaster recovery strategy for a critical application. They need a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 1 minute. Which AWS database service configuration meets these requirements?

Accepted Answer

Aurora Global Database. Aurora Global Database provides a fully managed cross-region disaster recovery solution with typical RPO of 1 second and RTO of 1 minute for regional failover, which meets the required RTO of 15 minutes and RPO of 1 minute. It uses storage-level replication that is asynchronous but very low-latency, and failover can be promoted to the secondary region in under a minute.

Answer

RDS MySQL with Multi-AZ and cross-region read replica

Answer

DynamoDB global tables

Answer

RDS PostgreSQL with cross-region read replica

Question 15

A company uses an Application Load Balancer (ALB) to distribute traffic to EC2 instances. The ALB is in us-east-1a and us-east-1b. They want to ensure that if one AZ fails, traffic is routed only to healthy instances in the other AZ. What configuration is necessary?

Accepted Answer

Enable cross-zone load balancing on the ALB. Cross-zone load balancing must be enabled on the ALB so that traffic can be distributed across instances in all AZs. By default, an ALB routes requests only to targets in the same Availability Zone as the requesting client. Enabling cross-zone load balancing allows the ALB to distribute traffic evenly across all registered targets in all enabled AZs, ensuring that if one AZ fails, traffic can be routed to healthy instances in other AZs. Option B is incorrect because health checks are already enabled by default and do not affect cross-AZ routing. Option C is incorrect because adding more AZs does not change the default AZ-affinity behavior; cross-zone load balancing must be explicitly enabled to utilize multiple AZs for failover.

Answer

Enable sticky sessions (session affinity)

Answer

Configure health checks on the target group

Answer

Add more subnets in additional AZs