DOP-C02 Resilient Cloud Solutions Practice Test 2 — 15 Questions

Question 1

A company runs a critical web application on EC2 instances behind an Application Load Balancer (ALB). The application stores session state in an Amazon DynamoDB table. During a recent traffic spike, users experienced session timeouts and the application became unavailable. Which design change would BEST improve resilience?

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

Accepted Answer

Move session state to Amazon ElastiCache for Redis with cluster mode disabled.. Moving session state to ElastiCache for Redis offloads read/write operations from DynamoDB during traffic spikes, reducing the risk of throttling and session timeouts. While cluster mode disabled means a single node, it provides in-memory caching that improves performance and can be scaled up to handle increased load, making the application more resilient compared to relying solely on DynamoDB for session state during spikes. Option B is incorrect because DynamoDB is inherently multi-AZ, and global tables are for multi-region deployments, not for handling traffic spikes or throttling. Option C (adding a read replica) does not address write bottlenecks or session persistence. Option D (increasing EC2 instance sizes) does not resolve the session state storage issue.

Answer

Enable DynamoDB global tables or use a Multi-AZ deployment for the table.

Answer

Add a read replica to the DynamoDB table.

Answer

Increase the EC2 instance sizes to handle more traffic.

Question 2

A company runs a stateless web application on AWS Lambda behind an Application Load Balancer (ALB). During a deployment, the team updates the Lambda function to a new version. Some users report seeing the old version of the application for several minutes after the deployment. What is the MOST likely cause?

Accepted Answer

The ALB target group is still pointing to the old Lambda function version due to connection draining.. When an ALB is used with Lambda, the ALB invokes a specific Lambda function version or alias. If the deployment updates the Lambda function but the ALB target group alias is not updated atomically, or if connection draining keeps old connections active, some requests may still be routed to the old version. This can cause users to see the old application for several minutes. Option A is wrong because Lambda versions are immutable, so gradual rollout is not related. Option B is wrong because Lambda@Edge is not used in this setup (the application runs behind an ALB, not CloudFront). Option C is wrong because CloudFront is not mentioned in the architecture—the traffic goes directly from ALB to Lambda.

Answer

The Lambda function versions are not immutable, causing a gradual rollout.

Answer

Lambda@Edge is overriding the function version at the edge locations.

Answer

Amazon CloudFront is caching the old response and has not been invalidated.

Question 3

A company is designing a disaster recovery strategy for its primary RDS for PostgreSQL database in us-east-1. The RTO is 15 minutes and RPO is 1 minute. Which solution meets these requirements?

Accepted Answer

Create a cross-Region read replica in the secondary Region and promote it during failover.. A cross-Region read replica can be promoted to a primary instance in a matter of minutes, meeting the 15-minute RTO, and replication lag is typically under 1 minute, satisfying the 1-minute RPO. Option B (AWS Backup every hour) provides an RPO of up to 1 hour, exceeding the requirement. Option C (Multi-AZ in same region) does not provide cross-Region failover. Option D (manual snapshots every 5 minutes) has a higher RPO than 1 minute and may not be promotable quickly enough.

Answer

Use AWS Backup to copy automated backups to the secondary Region every hour.

Answer

Deploy a Multi-AZ RDS instance and failover to the standby in the same region.

Answer

Take manual snapshots of the database every 5 minutes and copy them to the secondary Region.

Question 4

A company runs a microservices application on Amazon ECS with Fargate launch type. The application experiences intermittent failures when calling an external API. The errors are transient and usually resolve within a few seconds. How should the company improve resilience?

Accepted Answer

Implement retry logic with exponential backoff in the application code.. Implementing retry logic with exponential backoff handles transient failures gracefully. Option A is wrong because increasing timeouts could worsen latency without addressing the root cause. Option C is wrong because scaling up (increasing tasks) does not help with external API failures. Option D is wrong because async processing adds complexity and does not directly address transient API failures.

Answer

Increase the timeout of the external API call to 60 seconds.

Answer

Increase the number of tasks in the ECS service to handle failures.

Answer

Use an Amazon SQS queue to decouple the API call from the application.

Question 5

A company uses AWS CloudFormation to deploy a multi-tier application. During an update, the stack fails and rolls back. The rollback also fails, leaving the stack in UPDATE_ROLLBACK_FAILED state. The operations team needs to resolve this with minimal disruption. What is the MOST efficient approach?

Accepted Answer

Use the 'ContinueUpdateRollback' API or AWS Management Console to retry the rollback.. 'ContinueUpdateRollback' is designed to retry a failed rollback, often fixing transient issues and bringing the stack to a consistent state. Option B is wrong because manually modifying resources is error-prone and not recommended; AWS provides automated rollback tools. Option C is wrong because deleting a stack in UPDATE_ROLLBACK_FAILED state can be problematic and may cause resource loss; it is not the most efficient approach. Option D is wrong because change sets are for updates, not for resolving rollback failures; a change set cannot be applied to a stack in UPDATE_ROLLBACK_FAILED state without first continuing the rollback.

Answer

Manually modify the resources to match the previous stack state.

Answer

Delete the stack and recreate it from the original template.

Answer

Execute a change set to update the stack to the desired configuration.

Question 6

A company wants to ensure that its Amazon S3 bucket can withstand the loss of an entire AWS Availability Zone. Which configuration meets this requirement?

Accepted Answer

Use the S3 Standard storage class.. S3 Standard storage class automatically replicates data across at least three Availability Zones within an AWS Region, ensuring resilience against the loss of an entire AZ. Option B is incorrect because cross-Region replication replicates data to a different AWS Region, which provides geographic resilience but not specifically AZ resilience within the same Region. Option C is incorrect because S3 Versioning helps protect against accidental deletion or overwrite by preserving previous versions, but it does not provide data replication across AZs. Option D is incorrect because S3 One Zone-IA stores data in a single AZ, which would not withstand the loss of that AZ.

Answer

Configure cross-Region replication to another bucket.

Answer

Enable S3 Versioning on the bucket.

Answer

Use the S3 One Zone-IA storage class.

Question 7

A company runs a stateful application on EC2 instances in an Auto Scaling group. The application stores state on local instance storage. During a scaling event, users lose session data. How can the company make the application resilient without modifying the application code?

Accepted Answer

Use Elastic Block Store (EBS) volumes instead of instance store.. Using EBS volumes instead of instance store provides persistent storage that survives instance termination. By attaching an EBS volume to the EC2 instances and configuring the application to store state on that volume (e.g., through the same file path), the data is preserved even when instances are scaled in. This does not require modifying application code, only infrastructure configuration. Option A is incorrect because reducing the cooldown period does not prevent data loss; it only affects scaling speed. Option B is incorrect because sticky sessions route users to the same instance but do not preserve session data when that instance is terminated during scale-in. Option C is incorrect because larger instances reduce the frequency of scaling events but data loss still occurs when instances are terminated.

Answer

Reduce the Auto Scaling group cooldown period.

Answer

Enable sticky sessions on the Application Load Balancer.

Answer

Increase the instance size to reduce scaling events.

Question 8

A company uses Amazon Route 53 with a failover routing policy to direct traffic to an active and a standby endpoint. The health checks are configured to check the active endpoint every 10 seconds. During a recent outage, the failover took over 3 minutes to detect and switch. How can the company improve the failover time to under 1 minute?

Accepted Answer

Configure a Route 53 calculated health check that aggregates multiple fast health checks with a lower failure threshold.. Route 53 calculated health checks combine multiple health checks (e.g., 3 fast health checks each checking every 10 seconds) and allow you to set a lower failure threshold (e.g., 2 out of 3) to detect failure faster than a single health check. This reduces failover detection time to under 1 minute by aggregating results. Option B is wrong: additional health checks for the same endpoint would not improve detection time because they would all experience the same delay. Option C is wrong: the minimum health check interval for Route 53 is 10 seconds (fastest interval is 10 seconds, not 5). Option D is wrong: latency-based routing is for routing based on lowest latency, not for active/passive failover.

Answer

Add additional health checks for the same endpoint.

Answer

Reduce the health check interval to 5 seconds.

Answer

Change the routing policy to latency based.

Question 9

A company runs a critical application on Amazon EC2 instances in an Auto Scaling group. To ensure high availability, the instances are deployed across three Availability Zones. Which additional step should the company take to protect against a regional failure?

Accepted Answer

Deploy the application in a second AWS Region and use Route 53 with failover routing.. Deploying the application in a second AWS Region and using Route 53 with failover routing protects against a regional failure by redirecting traffic to the healthy region. Option A is incorrect because placing all instances in a single Availability Zone reduces availability and does not protect against regional failure. Option B is incorrect because EC2 Dedicated Hosts provide dedicated physical servers for licensing or compliance requirements, not regional resilience. Option C is incorrect because increasing the minimum size of the Auto Scaling group only affects capacity within the current region and does not mitigate a regional outage.

Answer

Place all instances in a single Availability Zone to simplify management.

Answer

Use EC2 Dedicated Hosts to ensure capacity.

Answer

Increase the minimum size of the Auto Scaling group to 10 instances.

Question 10

A company is designing a highly available architecture for a web application using AWS services. The application must be resilient to the failure of an entire AWS Region. Which TWO strategies should the company implement? (Choose TWO.)

Accepted Answer

Deploy the application in multiple AWS Regions and use Route 53 with failover routing policy.. Deploying to multiple regions with Route 53 failover provides cross-region disaster recovery. Option D is correct because using Amazon RDS Multi-AZ with cross-Region read replicas or Aurora Global Database ensures database resilience across regions. Option B is wrong because CloudFront alone does not provide compute failover. Option C is wrong because S3 cross-Region replication is for data, not compute. Option E is wrong because single-region Auto Scaling does not protect against region failure.

Answer

Use Amazon CloudFront with multiple origins in the same region.

Answer

Enable S3 cross-Region replication for static assets.

Answer

Use Auto Scaling groups in a single region with multiple Availability Zones.

Question 11

A company runs a containerized application on Amazon ECS with Fargate. The application needs to be resilient to Availability Zone failures. Which THREE actions should the company take? (Choose THREE.)

Accepted Answer

Configure the ECS service to spread tasks across multiple Availability Zones.. Spreading tasks across multiple Availability Zones ensures that an AZ failure does not impact all tasks, increasing resilience. Option C is correct because using a multi-AZ Amazon RDS or DynamoDB provides persistent data storage that survives AZ failures. Option D is correct because an Application Load Balancer with targets in multiple AZs distributes traffic and can route requests to healthy targets in other AZs if one fails. Option B is wrong because disabling managed service scaling reduces the application's ability to handle load changes and may impact availability. Option E is wrong because a single service discovery namespace does not provide AZ resilience; it only provides service discovery without redundancy across AZs.

Answer

Disable managed service scaling to avoid resource contention.

Answer

Use a single service discovery namespace for all tasks.

Question 12

A company is implementing a disaster recovery plan for its on-premises database using AWS. The plan must have a Recovery Time Objective (RTO) of 2 hours and a Recovery Point Objective (RPO) of 15 minutes. Which TWO AWS services should the company use? (Choose TWO.)

Accepted Answer

AWS Backup with cross-Region backup copy. AWS Database Migration Service (DMS) with ongoing replication continuously replicates database changes to AWS, achieving an RPO of 15 minutes. AWS Backup with cross-Region backup copy automates backups and enables recovery in another Region within 2 hours, meeting the RTO. Together, they satisfy the DR requirements. Option B (S3 with versioning) is for object storage, not database replication, and cannot achieve the RPO. Option A (Snowball Edge) is for offline data transfer, not real-time replication. Option E (Storage Gateway cached volumes) provides file/volume storage, not database replication.

Answer

AWS Snowball Edge

Answer

Amazon S3 with versioning

Answer

AWS Storage Gateway with cached volumes

Question 13

Refer to the exhibit. An IAM policy is attached to an IAM role used by an EC2 instance to manage other EC2 instances. The operations team reports that the instance can start and stop other instances but cannot terminate them. However, they also notice that the instance cannot describe instances in any region other than us-east-1. What is the reason for this behavior?

Accepted Answer

The Deny statement only applies to TerminateInstances, but the Allow statement for DescribeInstances is not restricted by region, so the issue must be elsewhere.. The policy explicitly allows ec2:DescribeInstances on all resources (*), which includes instances in any region. The Deny statement only applies to TerminateInstances and does not affect DescribeInstances. Therefore, based solely on this policy, the instance should be able to describe instances in any region. The reported issue must be due to another factor not shown in the exhibit (e.g., a service control policy, a trust policy, or a misconfiguration), making option D the most plausible explanation. Options A, B, and C are incorrect because DescribeInstances is not restricted by region in this policy, and DescribeRegions is not required for describing instances in other regions.

Answer

The policy does not include the ec2:DescribeRegions action, which is required to describe instances in other regions.

Answer

The Allow statement's Resource is set to '*' which only matches instances in the caller's region.

Answer

The Deny statement for TerminateInstances implicitly denies all other EC2 actions in regions other than us-east-1.

Question 14

Refer to the exhibit. An Auto Scaling group is configured with an Application Load Balancer. The group has a desired capacity of 2 instances spread across two Availability Zones. Recently, the application has been experiencing high error rates during deployments. The team suspects that new instances are being marked as healthy before they are fully ready. What should the team do to resolve this issue?

Accepted Answer

Change the HealthCheckType to ELB.. Changing the HealthCheckType to ELB makes the Auto Scaling group use the ALB's health checks, which can be configured with a health check path and threshold to verify that the application is actually responding before marking the instance healthy. Option A is incorrect because step scaling policies only adjust the desired capacity based on CloudWatch alarms; they do not affect how instances are marked healthy. Option B is incorrect because HealthCheckGracePeriod delays the start of health checks but does not ensure the application is ready; it merely postpones the health check decision. Option C is incorrect because increasing MaxSize does not impact the health check mechanism or readiness verification.

Answer

Add a step scaling policy to scale out more gradually.

Answer

Increase the HealthCheckGracePeriod to 600 seconds.

Answer

Increase the MaxSize to 10.

Question 15

Refer to the exhibit. A Lambda function uses the IAM role with the above policy. The function is configured to access a DynamoDB table MyTable and an RDS instance in a VPC. When invoked, the function fails with an error indicating it cannot describe VPC subnets. What is the MOST likely cause?

Accepted Answer

The Lambda function is missing permissions to describe VPC subnets and security groups.. When a Lambda function is configured to access a VPC, it requires permissions to describe VPC subnets and security groups to create elastic network interfaces. The provided IAM policy only allows ec2:CreateNetworkInterface and ec2:DeleteNetworkInterface, but not ec2:DescribeSubnets or ec2:DescribeSecurityGroups, causing the error. Option B is incorrect because the policy allows dynamodb:PutItem and UpdateItem, so the function can write to DynamoDB. Option C is incorrect because the policy allows creating network interfaces, so that is not the issue. Option D is incorrect because the error is about describing subnets, not about a DynamoDB resource policy.

Answer

The Lambda function does not have permission to write to DynamoDB.

Answer

The Lambda function cannot create network interfaces in the VPC.

Answer

The DynamoDB table's resource policy denies access from Lambda.