DOP-C02 Resilient Cloud Solutions Practice Test 1 — 15 Questions

Question 1

A company runs a critical web application on EC2 instances behind an Application Load Balancer (ALB) with Auto Scaling. During a recent traffic spike, the application became unavailable for 10 minutes. Analysis shows that the ALB's healthy host count dropped to zero because the instances failed health checks due to high CPU load. What is the MOST effective design change to improve resilience during future traffic spikes?

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

Accepted Answer

Use predictive scaling with a scheduled scaling policy for known peak times.. Predictive scaling uses historical traffic data to forecast future demand and proactively adjust capacity before a spike occurs. This prevents the CPU from reaching critical levels that cause health check failures, ensuring the ALB always has healthy hosts. Scheduled scaling alone would not adapt to unexpected spikes, but predictive scaling combined with dynamic scaling provides both proactive and reactive resilience.

Answer

Increase the instance size to handle higher load.

Answer

Configure step scaling policies based on CPU utilization.

Answer

Set a higher CPU threshold for health checks.

Question 2

A company uses DynamoDB global tables in two AWS Regions with strong consistency reads. They observe occasional write conflicts that are not being resolved automatically. The application uses DynamoDBMapper with optimistic locking. What should the DevOps engineer do to ensure conflict resolution?

Accepted Answer

Implement a custom conflict resolution using DynamoDB Streams and AWS Lambda.. DynamoDB global tables resolve conflicts automatically using last-writer-wins (LWW). However, if the application requires custom conflict resolution (e.g., to ensure only the latest version is applied or application-specific logic), LWW is insufficient. DynamoDB Streams can capture all updates, and a Lambda function can compare conflicting versions and apply the appropriate resolution. DynamoDBMapper's optimistic locking uses version attributes with conditional writes, but in global tables each replica may have a different version number; a conditional write in one region can succeed even if a newer write exists in another region, so it does not guarantee that the latest version wins.

Answer

Switch to eventual consistency reads to reduce conflicts.

Answer

Add a third global table region to increase redundancy.

Answer

Use conditional writes with a version number attribute to ensure updates are applied only to the latest version.

Question 3

A company wants to design a highly available web application using AWS services. The application must be resilient to the failure of an entire AWS Region. Which THREE components should the architecture include? (Choose THREE.)

Accepted Answer

Amazon Route 53 with a failover routing policy.. Option B is correct because Amazon Route 53 failover routing policies use health checks to automatically redirect DNS queries from a primary endpoint to a standby endpoint in another Region, which is essential for surviving a full Region outage. Option C is correct because deploying Auto Scaling groups in each Region ensures that compute capacity exists independently in the secondary Region and can scale to absorb traffic after failover, rather than relying on instances in the failed Region. Option E is correct because an Amazon RDS Multi-AZ deployment provides high availability within a Region, while a cross-Region read replica maintains a copy of the data in a second Region that can be promoted to a standalone primary database during a Regional disaster. Option A does not belong because an ALB is a Regional service; an ALB in only one Region cannot provide resilience if that entire Region fails. Option D does not belong because EC2 instances confined to a single Region are unavailable during a Region-wide outage and therefore cannot satisfy the cross-Region resiliency requirement.

Answer

An Application Load Balancer (ALB) deployed in one Region.

Answer

Amazon EC2 instances in a single Region.

Question 4

A company runs a critical web application on EC2 instances behind an Application Load Balancer (ALB) with Auto Scaling. During a recent traffic spike, the application became unavailable for 10 minutes. Analysis shows that the ALB's healthy host count dropped to zero because the instances failed health checks due to high CPU load. What is the MOST effective design change to improve resilience during future traffic spikes?

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

Accepted Answer

Use an RDS proxy (Amazon RDS Proxy) to pool and share database connections, and ensure the application uses the RDS cluster endpoint.. Amazon RDS Proxy maintains a warm connection pool to the database, so when the RDS Multi-AZ failover occurs, the proxy automatically reconnects to the new primary DB instance without requiring the application to re-establish connections. This eliminates the connection storm and the several-minute delay caused by the application's connection retry logic. The application must be configured to use the RDS Proxy endpoint (not the cluster endpoint) to benefit from this seamless failover.

Answer

Place all EC2 instances in a single AZ and use an Amazon Route 53 health check to reroute traffic to a standby environment in another AZ.

Answer

Deploy the RDS instance as a Single-AZ instance in the same AZ as the primary EC2 instances, and use read replicas for failover.

Answer

Configure an Application Load Balancer in front of the RDS instance to distribute connections across AZs.

Question 5

An AWS Lambda function that processes sensitive data writes objects to an S3 bucket. The security team requires that all objects be encrypted at rest using SSE-S3. The Lambda execution role uses the above IAM policy. Despite the policy, some objects are uploaded without server-side encryption. What is the most likely cause?

Accepted Answer

The Lambda function does not include the x-amz-server-side-encryption header in the PutObject request.. The IAM policy only allows the PutObject action when the request includes the `x-amz-server-side-encryption` header set to `AES256` (SSE-S3). If the Lambda function omits this header in its PutObject call, the request does not satisfy the IAM condition key `s3:x-amz-server-side-encryption`, and the policy denies the upload. However, the question states that objects are uploaded without encryption, which implies the policy is not being enforced as intended—likely because the Lambda function is not including the required header, and the bucket's default encryption or another mechanism is allowing the upload to succeed despite the policy.

Answer

The bucket has a default encryption policy that overrides the IAM policy.

Answer

The Lambda function is using a KMS key instead of SSE-S3.

Answer

The Lambda function is specifying a different encryption algorithm, such as aws:kms.

Question 6

Match each AWS CLI command to its function.

Accepted Answer

aws s3 sync: Syncs files to an S3 bucket. Correct matches: aws s3 sync syncs files to S3, aws ec2 describe-instances lists instances, aws cloudformation deploy deploys stacks, aws lambda invoke invokes functions. Common confusions arise from swapping these commands.

Answer

aws s3 sync: Deploys a CloudFormation stack

Answer

aws cloudformation deploy: Syncs files to an S3 bucket

Question 7

A company runs a critical web application on EC2 instances behind an Application Load Balancer (ALB) with Auto Scaling. During a recent traffic spike, the application became unavailable for 10 minutes. Analysis shows that the ALB's healthy host count dropped to zero because the instances failed health checks due to high CPU load. What is the MOST effective design change to improve resilience during future traffic spikes?

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 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.. A Route 53 calculated health check aggregates the results of multiple child health checks and can be configured with a lower failure threshold (e.g., 1) to trigger failover faster. By combining several fast health checks (each with a 10-second interval and 1 failure threshold), the calculated health check can detect an outage in as little as 10 seconds, well under the 1-minute requirement. This approach is specifically designed to improve failover responsiveness without relying on the minimum 10-second interval of standard health checks.

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 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 Backup with cross-Region backup copy (C) is correct because it provides automated, policy-driven backups of on-premises and AWS databases and can copy recovery points to another Region, enabling restoration within the 2-hour RTO and supporting frequent backup schedules that satisfy a 15-minute RPO. AWS Database Migration Service (DMS) with ongoing replication (D) is correct because continuous change data capture (CDC) replication keeps the target database synchronized with the source, so a failover can occur with minimal data loss (within 15 minutes) and quickly meet the 2-hour RTO. AWS Snowball Edge (A) is a physical data-transfer device for bulk migration, not a continuous replication or backup service, so it cannot meet a 15-minute RPO. Amazon S3 with versioning (B) only protects objects stored in S3 and does not provide database-level backup or replication for an on-premises database. AWS Storage Gateway with cached volumes (E) provides low-latency file/volume access with a local cache, but it is not a database replication or backup mechanism capable of meeting the stated RTO/RPO.

Answer

AWS Snowball Edge

Answer

Amazon S3 with versioning

Answer

AWS Storage Gateway with cached volumes

Question 10

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 contains an explicit Deny for ec2:TerminateInstances, which overrides any Allow, explaining why termination fails. The Allow statement for ec2:DescribeInstances has no region condition, so it should work in all regions. The reported inability to describe instances outside us-east-1 is therefore not caused by the policy shown; it must be due to another factor such as an SCP, permission boundary, or a different policy. Option D correctly identifies that the Deny only affects TerminateInstances and the Allow for DescribeInstances is unrestricted, so the described behavior cannot be explained by this policy alone.

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 11

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 Auto Scaling group's HealthCheckType to ELB makes the group rely on the load balancer's health checks (which respect the target group's health check path and thresholds) rather than only EC2 status checks. This ensures instances are only considered healthy — and thus kept in service — after the ALB confirms the application is responding correctly, preventing premature traffic routing during deployments.

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 12

A company runs a critical batch processing job on Amazon ECS using Fargate. The job must complete within 2 hours. If the job fails, it must be retried automatically up to 3 times. Which solution meets these requirements?

Accepted Answer

Use AWS Batch with a retry strategy set to 3 attempts. AWS Batch is designed for batch computing workloads and natively supports retry strategies. You can specify the number of retries (up to 3) in the job definition or submit job request. It also integrates with ECS/Fargate and can manage job queues and dependencies, making it the most straightforward solution for automatic retries.

Answer

Use AWS Step Functions with a task that invokes the ECS task, and configure a retry policy in the state machine

Answer

Use an Amazon ECS service with a desired count of 1 and enable automatic task replacement

Answer

Use AWS Lambda with a dead-letter queue and reprocess events

Question 13

A company uses AWS CodePipeline to deploy a web application. The pipeline includes a deploy action that uses AWS CloudFormation to update a stack. The deployment occasionally fails because of a transient resource limit error. Which automatic retry strategy should a DevOps engineer implement?

Accepted Answer

Set the deploy action's retry count to 3 in the pipeline definition. Configure the pipeline stage's on-failure retry configuration (RetryConfiguration) to automatically retry using retryMode FAILED_ACTIONS. This lets CodePipeline automatically re-run only the failed action(s) in the stage a single time when a transient error like a resource limit occurs, without restarting earlier stages. Note: CodePipeline supports only one automatic retry attempt per stage failure, not a configurable retry count.

Answer

Use an AWS Step Function to orchestrate the deployment with retry logic

Answer

Modify the CloudFormation stack to include a retry policy

Answer

Configure the pipeline to retry the entire pipeline execution on failure

Question 14

A company has a critical application running on EC2 instances in an Auto Scaling group across two Availability Zones. The application uses an EBS volume for local caching. The company wants to ensure that if an instance fails, the cache data is not lost and the replacement instance can use it. Which solution meets this requirement?

Accepted Answer

Use Amazon EFS instead of EBS for the cache. Amazon EFS is a shared, elastic file system that can be mounted concurrently by multiple EC2 instances across Availability Zones, making it the correct choice for cache data that must survive instance failure and be accessible to a replacement instance. EBS volumes are tied to a single Availability Zone and, with the exception of Multi-Attach (which is limited to io1/io2 in the same AZ), cannot be shared across instances or AZs. Snapshots can restore data but require manual or scripted intervention and do not provide continuous availability.

Answer

Configure the Auto Scaling group to use a launch template that attaches the same EBS volume to new instances

Answer

Take periodic EBS snapshots and create a new volume from the snapshot for the replacement instance

Answer

Use an EBS Multi-Attach volume and attach it to all instances in the Auto Scaling group

Question 15

A company is designing a disaster recovery plan for a critical application that uses Amazon RDS for MySQL with Multi-AZ. The RPO must be less than 1 minute and RTO less than 15 minutes. The primary Region is us-east-1. Which TWO steps should the company take to meet these requirements?

Accepted Answer

Create a cross-Region read replica of the RDS instance in the secondary Region. Option C is correct because a cross-Region read replica continuously replicates data asynchronously from the primary RDS for MySQL instance to a secondary Region, providing a low-latency, near-real-time copy that can satisfy an RPO of less than 1 minute. Option D is correct because promoting the cross-Region read replica to a standalone primary is the standard RDS failover mechanism for cross-Region DR, and automating it with Lambda keeps the RTO within the 15-minute target. Option A is not appropriate because RDS does not support snapshots every 30 seconds, and manual snapshot copy latency would not reliably meet a sub-1-minute RPO. Option B is not sufficient because Multi-AZ only provides high availability within a single Region and does not protect against a Region-wide failure. Option E is not suitable because automated backups with cross-Region copy have much longer intervals and restore times, so they cannot meet the sub-1-minute RPO and 15-minute RTO requirements.

Answer

Take manual snapshots of the RDS instance every 30 seconds and copy them to the secondary Region

Answer

Enable Multi-AZ in the primary Region

Answer

Enable automated backups with cross-Region copy enabled to the secondary Region