DOP-C02 Resilient Cloud Solutions Practice Test 6 — 15 Questions

Question 1

A startup runs a web application on EC2 instances behind an Application Load Balancer. They want to improve resilience by distributing instances across multiple Availability Zones. Currently, all instances are in us-east-1a. They create a launch template and an Auto Scaling group with a desired capacity of 2. They configure the Auto Scaling group to use two subnets: one in us-east-1a and one in us-east-1b. However, after updating, all instances remain in us-east-1a. What is the most likely reason?

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

Accepted Answer

The instance type is not available in us-east-1b.. The most likely reason is that the instance type is not available in us-east-1b. If the instance type is not supported in that Availability Zone, the Auto Scaling group cannot launch instances there, so it will launch all instances in the AZ where the instance type is available (us-east-1a). This is a common issue when using specialized instance types that are not available in all AZs.

Answer

The Auto Scaling group's subnet configuration was not updated to include the new subnet.

Answer

The new subnet in us-east-1b has no route to the internet.

Answer

The launch template specifies a single subnet in us-east-1a.

Question 2

A company runs a multi-tier web application on AWS. The application consists of an Application Load Balancer, EC2 instances in an Auto Scaling group, and an Amazon RDS Multi-AZ DB instance. The application experiences intermittent failures when the RDS primary instance fails over to the standby. The engineer needs to ensure that the application handles failover gracefully without manual intervention.

Accepted Answer

Use Amazon RDS Proxy to pool and reuse database connections, which reduces connection churn during failover.. Using a proxy like ProxySQL or configuring the application to use the RDS endpoint (which automatically points to the current primary) helps handle failover. Additionally, enabling RDS connection pooling or using Lambda to update the application can help, but the simplest is to use the instance endpoint with a retry mechanism.

Answer

Modify the application to use DNS caching with a TTL of 300 seconds to avoid stale DNS records.

Answer

Configure the Application Load Balancer to perform health checks on the RDS instance.

Answer

Enable Multi-AZ on the Auto Scaling group to ensure EC2 instances are in multiple AZs.

Question 3

A gaming company runs a real-time multiplayer game on AWS using Amazon EC2 instances in an Auto Scaling group behind a Network Load Balancer. The game state is stored in Amazon ElastiCache for Redis. The team needs to ensure that the architecture can survive a regional failure with minimal data loss and recovery time. The RTO is 15 minutes and RPO is 5 minutes. The game currently uses a single Redis cluster in us-east-1.

Accepted Answer

Configure Amazon ElastiCache for Redis with Global Datastore to replicate data to a second region.. Option C is correct because ElastiCache for Redis Global Datastore is the AWS feature designed for cross-region replication of a Redis cluster, providing a secondary cluster in another region with typically sub-second replication lag, which satisfies the 5-minute RPO for a regional failover. Option E is correct because surviving a regional failure requires compute capacity in the secondary region, so a second Auto Scaling group of EC2 instances must exist there, and Route 53 failover routing (with health checks) automatically redirects players to the healthy region, meeting the 15-minute RTO. Option A is not correct because Multi-AZ only protects against an Availability Zone failure within us-east-1 and does nothing for a full regional outage. Option B is not correct because disabling cluster mode is a scaling/sharding decision that does not provide any cross-region replication or regional failover capability. Option D is not correct because writing to a local Redis replica in the secondary region and syncing back is not a supported ElastiCache replication model and would risk data divergence and loss, violating the RPO.

Answer

Enable Multi-AZ on the ElastiCache cluster to improve availability within the region.

Answer

Use Amazon ElastiCache for Redis with cluster mode disabled to simplify failover.

Answer

Configure the application to write to the local Redis replica in the secondary region and then sync back.

Question 4

A company runs a critical order-processing system on an Amazon EC2 Auto Scaling group that spans three Availability Zones. The group is configured with a minimum capacity of 6, maximum of 12, and uses a target tracking scaling policy based on average CPU utilization. During a recent event, one Availability Zone became impaired for 45 minutes. The Auto Scaling group did not launch replacement instances in the remaining healthy zones because the desired capacity was already satisfied by the impaired instances, which were still passing health checks at the EC2 level. The company wants the application to automatically maintain capacity in healthy Availability Zones when an AZ is impaired, without manual intervention. Which solution meets these requirements?

Accepted Answer

Enable the Availability Zone rebalancing feature on the Auto Scaling group and set the group's desired capacity to distribute instances evenly across the healthy zones.. Availability Zone rebalancing is the Auto Scaling feature that keeps capacity evenly distributed across enabled Availability Zones. When an AZ becomes impaired and its instances are no longer usable, the group detects the imbalance and launches instances in the remaining healthy zones, restoring capacity automatically. This is the intended mechanism for maintaining resilience during AZ-level failures without manual steps.

Answer

Configure the Auto Scaling group to use Elastic Load Balancing health checks and attach the instances to a target group with cross-zone load balancing enabled.

Answer

Create a second Auto Scaling group in each Availability Zone and use an Application Load Balancer with a single target group.

Answer

Enable Auto Scaling group capacity rebalancing and configure the group to use only the two healthy Availability Zones.

Question 5

A company uses AWS CloudFormation to deploy a three-tier application. The web tier runs on an Auto Scaling group of EC2 instances behind an Application Load Balancer. The application tier runs on another Auto Scaling group. The database tier uses Amazon RDS for PostgreSQL with a read replica. During a recent incident, the primary database instance failed over to the standby, but the application tier continued to connect to the old primary endpoint because the connection string was hardcoded in the user data script. The company wants to ensure that the application automatically connects to the new primary after a failover without manual intervention. Which solution should a DevOps engineer implement?

Accepted Answer

Configure the application to connect using the RDS primary endpoint (the DNS name that points to the current primary) and rely on the automatic DNS update after failover.. Amazon RDS Multi-AZ deployments provide a primary endpoint that automatically points to the current primary DB instance. When a failover occurs, the DNS record for the primary endpoint is updated to the new primary, allowing applications that use this endpoint to reconnect automatically. This is the simplest and most reliable solution, requiring no manual intervention or additional services.

Answer

Create an Amazon Route 53 CNAME record that points to the RDS primary endpoint and configure the application to use the CNAME.

Answer

Store the database connection string in AWS Systems Manager Parameter Store and have the application retrieve it at startup, then use the RDS primary endpoint.

Answer

Configure the application to use the RDS instance endpoint instead of the cluster endpoint and update the connection string in the user data script.

Question 6

A DevOps engineer is designing a disaster recovery strategy for a stateful application that uses an Amazon Aurora MySQL cluster. The RPO is 5 minutes and the RTO is 15 minutes. The primary cluster is in us-east-1. The engineer needs to ensure that the application can fail over to another region with minimal data loss and rapid recovery. Which solution should the engineer implement?

Accepted Answer

Set up an Aurora global database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. During a disaster, promote the secondary cluster to a standalone cluster.. Aurora global database provides cross-region replication with minimal lag (typically under 1 second) and allows a secondary cluster to be promoted to a standalone cluster in under a minute. This meets the RPO of 5 minutes and RTO of 15 minutes. It is the native and recommended solution for cross-region disaster recovery for Aurora.

Answer

Configure an Aurora global database with the primary cluster in us-east-1 and a secondary cluster in us-west-2. Enable write forwarding on the secondary cluster.

Answer

Use AWS Database Migration Service (DMS) to continuously replicate data from the Aurora cluster in us-east-1 to an Aurora cluster in us-west-2. Switch the application to the secondary cluster during a disaster.

Answer

Create an Aurora read replica in us-west-2 using binary log replication. Promote the replica to a standalone cluster during a disaster.

Question 7

A company runs a stateless web application on Amazon EC2 instances behind an Application Load Balancer. The application stores user-uploaded files in an Amazon S3 bucket. The company wants to ensure that the application remains available even if an entire AWS Region becomes unavailable. The RTO is 2 hours and the RPO is 15 minutes. Which strategy meets these requirements with the LEAST operational overhead?

Accepted Answer

Use AWS Elastic Disaster Recovery to replicate EC2 instances to a second Region, and enable S3 Cross-Region Replication for the S3 bucket.. AWS Elastic Disaster Recovery provides continuous replication of EC2 instances to a second Region with minimal operational overhead, enabling recovery within the 2-hour RTO. S3 Cross-Region Replication replicates objects with a 15-minute RPO. Together, they meet the requirements while minimizing management effort compared to active-active or manual snapshot approaches.

Answer

Configure Amazon Route 53 failover routing to a standby Region that runs a scaled-down version of the application, and use S3 Cross-Region Replication for the S3 bucket.

Answer

Take daily Amazon EBS snapshots and copy them to a second Region, and use S3 Cross-Region Replication for the S3 bucket.

Answer

Deploy the application in two Regions with an active-active configuration, using Amazon Route 53 weighted routing and S3 Cross-Region Replication.

Question 8

A company runs a stateful application on a single EC2 instance in a single Availability Zone. The application writes data to an attached Amazon EBS volume. The company wants to improve resilience by implementing a disaster recovery strategy that can survive the loss of the entire Availability Zone. The RTO is 15 minutes and the RPO is 5 minutes. The company wants a cost-effective solution that minimizes operational overhead. Which solution meets these requirements?

Accepted Answer

Create a snapshot schedule for the EBS volume every 5 minutes using Amazon Data Lifecycle Manager, and store snapshots in a different Availability Zone. In case of AZ failure, restore the volume from the latest snapshot and launch an EC2 instance in another AZ.. Using Amazon Data Lifecycle Manager to automate EBS snapshots every 5 minutes provides a low RPO and stores snapshots in S3, which is accessible across AZs. Restoring from a snapshot and launching an instance in another AZ can be automated with scripts or AWS Systems Manager, meeting the 15-minute RTO. This solution is cost-effective and requires minimal ongoing management, making it ideal for this scenario.

Answer

Set up an AWS Storage Gateway file gateway in the primary AZ and replicate data to Amazon S3. In case of failure, use the file gateway in another AZ to serve data.

Answer

Use Amazon EBS Multi-Attach to attach the volume to EC2 instances in two Availability Zones simultaneously, and configure the application to write to both instances.

Answer

Enable EBS volume replication to a second Availability Zone using Amazon EBS direct APIs, and attach the replica volume to a standby EC2 instance.

Question 9

A company runs a stateless web application on Amazon EC2 instances in an Auto Scaling group across three Availability Zones. The application is behind an Application Load Balancer (ALB). The DevOps team wants to ensure that the application remains available even if an entire Availability Zone fails. The team has already configured the Auto Scaling group to span three Availability Zones. Which two additional configurations should the DevOps engineer implement to meet this requirement? (Choose two.)

Accepted Answer

Enable cross-zone load balancing on the ALB to distribute traffic evenly across all registered targets in all enabled Availability Zones.. To ensure availability if an AZ fails, the ALB must have subnets in multiple AZs, and cross-zone load balancing should be enabled so that traffic is distributed across all healthy targets in all AZs. The Auto Scaling group already spans three AZs, so these two configurations are necessary for the load balancer to continue routing traffic to the remaining AZs.

Answer

Set up an Amazon Route 53 health check to monitor the ALB and fail over to a static S3 website if the ALB becomes unhealthy.

Answer

Enable sticky sessions on the ALB to ensure that users are routed to the same instance for the duration of their session.

Answer

Configure the Auto Scaling group to use a launch template with multiple instance types to improve availability.

Question 10

A company runs a serverless application using AWS Lambda functions that process messages from an Amazon SQS queue. The application must be resilient to failures and ensure that messages are not lost if a Lambda function fails. The company wants to minimize the number of times a message is processed more than once. Which configuration should the DevOps engineer implement?

Accepted Answer

Configure the SQS queue as an event source with a batch size of 10, enable partial batch responses, and set the function's maximum retry attempts to 2.. Enabling partial batch responses allows the Lambda function to return only the failed messages for retry, so successful messages are not reprocessed. Setting a maximum retry attempts of 2 limits the number of retries, reducing duplicate processing. This configuration ensures failed messages are retried while minimizing unnecessary reprocessing, meeting the resilience and efficiency requirements.

Answer

Configure the SQS queue as an event source for the Lambda function with a batch size of 10 and set the function's reserved concurrency to 0.

Answer

Configure the SQS queue as an event source with a batch size of 10, enable dead-letter queues for the Lambda function, and set the queue's visibility timeout to 30 seconds.

Answer

Configure the SQS queue as an event source with a batch size of 1 and set the function's timeout to 15 minutes.

Question 11

A company uses AWS Lambda functions to process messages from an Amazon SQS queue. The Lambda function is configured with a batch size of 10 and a maximum of 5 concurrent executions. During peak hours, the queue length grows rapidly, and messages are not processed in a timely manner. The DevOps engineer needs to increase the processing throughput while ensuring that messages are not lost. What should the engineer do?

Accepted Answer

Increase the Lambda function's batch size to 100 and adjust the maximum concurrency if needed.. Increasing the batch size allows the Lambda function to process more messages per invocation, which directly increases throughput. While concurrency also affects throughput, the batch size is a key lever. Adjusting concurrency may also be needed, but increasing the batch size is the most direct action to improve message processing rate.

Answer

Increase the Lambda function's reserved concurrency to 100.

Answer

Increase the SQS queue's visibility timeout to match the Lambda function's timeout.

Answer

Configure the SQS queue as a FIFO queue to ensure ordered processing.

Question 12

A DevOps engineer manages a multi-account AWS environment using AWS Organizations. The company requires that all Amazon S3 buckets in all accounts have server access logging enabled. The engineer needs to enforce this requirement and automatically remediate any non-compliant buckets. Which solution should the engineer implement?

Accepted Answer

In the AWS Organizations management account, enable AWS Config and create an organization conformance pack that includes the s3-bucket-logging-enabled rule. Configure automatic remediation using an AWS Lambda function.. AWS Organizations conformance packs allow centralized deployment of AWS Config rules across all accounts. By including the s3-bucket-logging-enabled rule and configuring automatic remediation with a Lambda function, the engineer can enforce and remediate logging across the organization. This is the most efficient and scalable solution.

Answer

Use AWS CloudFormation StackSets to deploy an AWS Config rule and an AWS Lambda remediation function to all accounts in the organization. Configure the Config rule with automatic remediation.

Answer

Use AWS Service Control Policies (SCPs) to deny the creation of S3 buckets without logging enabled.

Answer

Create an AWS Config rule in each account using the s3-bucket-logging-enabled managed rule. Configure an AWS Lambda function as a custom remediation action that enables logging on non-compliant buckets.

Question 13

A company's application runs on EC2 instances in a single Availability Zone. The operations team wants to improve resilience without redesigning the application. Which action is the MOST effective?

Accepted Answer

Deploy EC2 instances across multiple Availability Zones using an Auto Scaling group.. Deploying EC2 instances across multiple Availability Zones (AZs) using an Auto Scaling group is the most effective action because it eliminates the single point of failure at the AZ level. If one AZ experiences an outage, the Auto Scaling group automatically launches replacement instances in the remaining healthy AZs, ensuring application availability without requiring any application-level changes. This directly addresses the goal of improving resilience by leveraging AWS's fault-isolated infrastructure.

Answer

Use a larger instance type to handle more traffic.

Answer

Enable EC2 Auto Recovery to automatically restart the instance if it fails.

Answer

Place the instance in a placement group to ensure low latency.

Question 14

A company uses a third-party backup solution to back up its EC2 instances daily. The backups are stored in an S3 bucket with default settings. The company wants to ensure that backups are protected from accidental deletion and are available for at least one year. Which combination of S3 features should the DevOps engineer implement?

Accepted Answer

Enable S3 Object Lock with Governance mode and a retention period of 365 days, and set a lifecycle policy to transition to S3 Glacier Deep Archive after 30 days.. S3 Object Lock with Governance mode prevents objects from being deleted or overwritten by any user (including the root user) for the specified retention period of 365 days, meeting the one-year availability requirement. The lifecycle policy to transition to S3 Glacier Deep Archive after 30 days reduces storage costs while still keeping the data accessible for retrieval within 12 hours, which is acceptable for backup retention. This combination ensures immutability and cost-effective long-term storage.

Answer

Enable MFA Delete and set a lifecycle policy to transition to S3 Glacier after 30 days.

Answer

Enable versioning and set a lifecycle policy to expire noncurrent versions after 365 days.

Answer

Enable cross-Region replication to a bucket with versioning enabled.

Question 15

A company runs a stateful web application on EC2 instances behind a Network Load Balancer (NLB) in a single Availability Zone. The application stores session state locally on the instance. The company wants to achieve high availability across multiple AZs with minimal application changes. What should the DevOps engineer do?

Accepted Answer

Replace the NLB with an ALB and enable sticky sessions (session affinity) using the ALB's cookie.. Replacing the NLB with an ALB and enabling sticky sessions (session affinity) using the ALB's cookie allows the stateful web application to maintain session state across multiple AZs without modifying the application code. The ALB generates a cookie (AWSALB) that binds a client's session to a specific target instance, ensuring subsequent requests from the same client are routed to the same EC2 instance. This achieves high availability across AZs with minimal changes, as the application continues to store session state locally on the instance.

Answer

Add more AZs and configure the NLB with cross-zone load balancing.

Answer

Replace the NLB with an ALB and use ElastiCache for session storage.

Answer

Use a Multi-AZ RDS instance to store session state.