Resilient Cloud Solutions — DOP-C02 Practice Quiz

Question 1

A company runs a stateless web application on EC2 instances behind an Application Load Balancer (ALB) spread across three Availability Zones. An Auto Scaling group maintains 3 instances per AZ. During a recent single-AZ impairment, monitoring showed that clients connected through the affected AZ received elevated latency and some 5xx errors even though healthy instances existed in the other two AZs. The DevOps team wants to ensure that a single-AZ failure does not degrade the user experience, with minimal ongoing management. Which action BEST addresses this requirement?

Accepted Answer

Confirm cross-zone load balancing is enabled on the ALB so requests are distributed evenly to healthy targets in all AZs regardless of which AZ received the request.

Answer

Enable ALB health checks with a lower unhealthy threshold and rely on the Auto Scaling group to replace failed instances in the impaired AZ.

Answer

Configure Route 53 latency-based routing with health checks pointing to per-AZ ALB nodes so traffic avoids the impaired AZ.

Answer

Increase the Auto Scaling group desired capacity and use a target tracking policy on ALB request count to add capacity when an AZ fails.

Question 2

A media streaming company runs a stateful session service on an EC2 Auto Scaling group behind a Network Load Balancer. During scale-in events, users report abruptly dropped streams because instances terminate while active sessions are still in progress. Each session can last up to 8 minutes and the application can persist session state to DynamoDB if given time. The DevOps team must ensure that instances chosen for termination complete in-flight sessions before shutting down, without changing the streaming protocol. What is the MOST appropriate way to achieve this?

Accepted Answer

Add an Auto Scaling lifecycle hook for the terminating state that pauses the instance in Terminating:Wait, and use a script on the instance to drain sessions and call CompleteLifecycleAction before the heartbeat timeout expires.

Answer

Increase the NLB deregistration delay (connection draining) to 600 seconds so sessions finish before the instance is removed from the target group.

Answer

Enable instance scale-in protection on all instances in the Auto Scaling group so that no instance with active sessions is ever terminated.

Answer

Configure a target tracking scaling policy with a longer cooldown period to delay scale-in until sessions naturally complete.

Question 3

A media company runs a stateless web tier on an EC2 Auto Scaling group behind an ALB. During flash-sale events, traffic ramps sharply then drops in irregular waves. The team currently uses simple scaling policies with CloudWatch alarms on average CPU, plus a 300-second cooldown period. They observe that the group repeatedly scales out and scales in within short intervals (flapping), causing instances to churn and users to hit brief connection errors while capacity settles. The team wants scaling to respond quickly to sustained demand while avoiding rapid oscillation, with minimal manual tuning of thresholds. Which change best meets these requirements?

Accepted Answer

Replace the simple scaling policies with a target tracking scaling policy on average CPU utilization, allowing Auto Scaling to compute the required capacity and manage the scaling thresholds automatically.

Answer

Increase the cooldown period to 1800 seconds so the group cannot scale in or out more than once every 30 minutes during the event.

Answer

Switch to scheduled scaling that sets a fixed desired capacity for the duration of every flash-sale window based on the previous event's peak.

Answer

Add a second simple scaling policy on network throughput and lower the CPU alarm threshold so the group reacts faster to traffic spikes.

Question 4

A financial services company runs a stateless order-matching service on an EC2 Auto Scaling group behind an Application Load Balancer. During market-open bursts, demand spikes within seconds. The application AMI is large and requires roughly 6 minutes to boot, run configuration scripts, and warm its JVM cache before it can pass ALB health checks. Scale-out driven by target-tracking on request count is too slow, causing dropped orders during the first few minutes of each spike. The team wants to reduce scale-out latency without permanently running (and paying for full price on) many idle instances. Which approach best meets these requirements?

Accepted Answer

Configure an Auto Scaling group warm pool with instances kept in the Stopped state, using lifecycle hooks to complete initialization before stopping so warmed instances can be quickly returned to service.

Answer

Increase the target-tracking metric's target value and set a shorter cooldown period so the group launches instances more aggressively during spikes.

Answer

Replace target-tracking with scheduled scaling that sets the desired capacity to the peak value 10 minutes before market open every day.

Answer

Enable predictive scaling only, relying on its machine-learning forecast to provision the exact number of instances needed at each moment.

Question 5

A financial services company runs a mission-critical application on an Amazon Aurora MySQL-Compatible cluster. During a faulty deployment, an application bug executed a bad UPDATE statement that silently corrupted several tables. The problem was discovered 45 minutes later. The team needs to recover the database to the exact state moments before the corruption with the least amount of downtime and without provisioning a new cluster endpoint that would require application reconfiguration. Which approach best meets these requirements?

Accepted Answer

Use Aurora Backtrack to rewind the existing cluster to a timestamp just before the bad UPDATE executed.

Answer

Restore the most recent automated snapshot to a new Aurora cluster and update the application connection string to the new endpoint.

Answer

Perform a point-in-time restore (PITR) to a new cluster at the timestamp before corruption and repoint the application.

Answer

Promote an Aurora Replica to a standalone cluster and replay binary logs up to the point before the corruption.

Question 6

A financial services company runs a critical transaction processing application on an Amazon Aurora PostgreSQL cluster in us-east-1. Compliance requires an RPO of under 1 second and an RTO of under 5 minutes in the event of a full regional outage, and the disaster recovery region (us-west-2) must be able to accept application traffic quickly. The DevOps team must automate failover so that operators are not required to reconfigure the database endpoint manually during a regional event. Which approach BEST meets these requirements?

Accepted Answer

Configure an Aurora Global Database with a secondary cluster in us-west-2, and use a Route 53 health check with an Amazon EventBridge rule that triggers a Lambda function to perform a managed planned/unplanned failover promoting the secondary.

Answer

Enable automated cross-region snapshot copy of the Aurora cluster to us-west-2 every hour, and restore the most recent snapshot with a Lambda function when CloudWatch detects the primary is unhealthy.

Answer

Deploy a Multi-AZ Aurora cluster in us-east-1 with read replicas across three Availability Zones, relying on Aurora's automatic AZ failover to satisfy the regional recovery requirement.

Answer

Use AWS Database Migration Service with ongoing change data capture replication from us-east-1 to a standalone Aurora cluster in us-west-2, and switch the application connection string manually during an outage.

Question 7

A financial services company must implement a centralized, automated disaster recovery strategy for a fleet of EC2 instances, EBS volumes, and DynamoDB tables spread across multiple accounts in an AWS Organization. Compliance requires that all backups be retained for 7 years, be immutable (protected against deletion even by administrators), and be copied to a second AWS Region for DR. The team wants to minimize custom scripting and manage the policy centrally. Which approach best meets these requirements?

Accepted Answer

Use AWS Backup with a delegated administrator account, create a backup policy in AWS Organizations that assigns backup plans with cross-Region copy actions, and enable AWS Backup Vault Lock in compliance mode on the destination vaults.

Answer

Write Lambda functions triggered by EventBridge in each account to create EBS snapshots and DynamoDB exports, copy them cross-Region, and apply S3 Object Lock for immutability.

Answer

Use AWS Backup in each account independently with local backup plans, then use Data Lifecycle Manager to copy snapshots to the second Region and enable Vault Lock in governance mode.

Answer

Enable AWS Backup with cross-Region copy and apply Vault Lock in governance mode centrally through a delegated administrator, relying on SCPs to prevent deletion.

Question 8

A financial services company runs a monolithic web application on EC2 behind an ALB in us-east-1, backed by an RDS PostgreSQL Multi-AZ database. Compliance requires an RTO of 15 minutes and an RPO of 5 minutes for a regional disaster in a secondary region (us-west-2). The team wants to minimize steady-state cost while still meeting these targets, and they want failover to be automated as much as possible. Which disaster recovery strategy best meets these requirements?

Accepted Answer

Implement a warm standby: run a scaled-down but always-on copy of the application fleet and an RDS cross-region read replica in us-west-2, with Route 53 health checks and automation to scale up and promote the replica on failover.

Answer

Implement a backup-and-restore strategy: take automated RDS snapshots copied to us-west-2 and store AMIs there, then use a runbook to launch the full stack from scratch during a disaster.

Answer

Implement a pilot light: keep only the RDS cross-region read replica running in us-west-2 with no application servers, and rely on manual invocation of a runbook that boots the fleet and promotes the replica during a disaster.

Answer

Implement a multi-site active/active deployment: run the full-scale application fleet and an Aurora Global Database writer in both regions, serving live traffic from both with Route 53 latency routing.

Question 9

A financial services company runs a trading dashboard backed by a DynamoDB table in us-east-1. Leadership requires that the application continue accepting both reads and writes with near-zero data loss and sub-minute recovery if the entire us-east-1 region becomes unavailable. Application traffic is served from ALBs in both us-east-1 and eu-west-1 fronted by Route 53. Which approach best meets the availability and RPO/RTO requirements with the least operational effort?

Accepted Answer

Convert the table to a DynamoDB global table with a replica in eu-west-1, and configure Route 53 health checks with failover routing so traffic shifts to the eu-west-1 endpoint automatically.

Answer

Enable point-in-time recovery (PITR) on the table and use an EventBridge-triggered Lambda to restore the latest snapshot into eu-west-1 when a CloudWatch alarm detects the outage.

Answer

Enable DynamoDB on-demand backups every 5 minutes and copy them to eu-west-1 with AWS Backup cross-region copy, restoring the most recent backup during a regional failure.

Answer

Deploy a read replica of the DynamoDB table in eu-west-1 and promote it to a primary using a runbook executed by the on-call engineer when us-east-1 fails.

Question 10

A financial services company runs a DynamoDB table storing transaction records. Compliance requires that any point in the last 35 days must be recoverable to meet a tight RPO, AND that specific quarter-end table snapshots be retained immutably for 7 years for audit purposes. The DevOps team wants to automate both requirements with the least operational overhead while minimizing recovery time for the daily use case. Which approach best satisfies both requirements?

Accepted Answer

Enable DynamoDB Point-in-Time Recovery (PITR) for the 35-day continuous recovery window, and use AWS Backup with a scheduled backup plan and a cold-storage/retention lifecycle to capture and retain quarter-end backups for 7 years.

Answer

Enable PITR only, and rely on its continuous backups to satisfy both the 35-day and 7-year retention requirements.

Answer

Schedule a Lambda function via EventBridge to export the table to S3 daily and quarterly, applying S3 lifecycle rules to expire objects after 7 years.

Answer

Use AWS Backup with a continuous backup rule set to a 7-year retention period to cover both the 35-day RPO and the long-term audit retention.

Question 11

A financial services company runs a critical order-processing application backed by a DynamoDB table in us-east-1. Compliance requires the ability to recover the table to any point within the last 24 hours (RPO of 5 minutes) and to restore into a separate DR region (us-west-2) within an RTO of 2 hours in the event of a regional outage. The team wants a fully managed, low-operational-overhead solution that also protects against accidental writes or deletes. Which approach best meets these requirements?

Accepted Answer

Enable DynamoDB Point-in-Time Recovery (PITR) on the table and, when needed, use the built-in restore capability to restore the table to a new table in us-west-2 for the desired timestamp.

Answer

Configure DynamoDB global tables between us-east-1 and us-west-2 and rely on multi-region replication to recover from accidental writes and regional failures.

Answer

Schedule AWS Backup on-demand jobs every 5 minutes to back up the table and copy each recovery point to a vault in us-west-2.

Answer

Enable DynamoDB Streams and write a Lambda function that continuously exports item-level changes to an S3 bucket in us-west-2 for manual replay during recovery.

Question 12

A DevOps team manages a stateless web tier on an EC2 Auto Scaling group behind an Application Load Balancer. They deploy a new AMI using an instance refresh with a minimum healthy percentage of 90% and a health check grace period of 300 seconds. During the refresh, the new AMI contains a misconfiguration that causes instances to pass EC2 status checks but fail the ALB target group HTTP health check. The team wants the instance refresh to detect these failures and stop replacing instances automatically before the entire fleet is cycled. Which configuration change ensures the instance refresh halts when the new instances are unhealthy?

Accepted Answer

Set the Auto Scaling group health check type to ELB and enable checkpoints so the instance refresh evaluates ELB health during each phase.

Answer

Increase the health check grace period to 900 seconds so the ALB has more time to mark the new instances healthy before continuing.

Answer

Lower the minimum healthy percentage to 50% so more instances are replaced simultaneously and failures surface faster.

Answer

Attach a scheduled scaling action that scales in the group if CloudWatch UnHealthyHostCount exceeds zero during the deployment window.

Question 13

A company runs a stateless order-processing microservice on Amazon ECS with the Fargate launch type. The service must remain available even if an entire Availability Zone becomes impaired. Currently the service definition specifies a desired count of 6 tasks running in a cluster spanning three AZs, but during a recent AZ outage most tasks were unavailable because they happened to be concentrated in the failed AZ. Which change most effectively ensures tasks are automatically redistributed and remain balanced across AZs after failures and scaling events?

Accepted Answer

Configure the ECS service to use the 'spread' task placement strategy across the 'attribute:ecs.availability-zone' field so tasks are evenly distributed across AZs.

Answer

Increase the desired task count to 12 and enable Service Auto Scaling based on CPU utilization to compensate for lost tasks.

Answer

Switch the launch type to EC2 and configure a 'binpack' placement strategy to consolidate tasks and improve density.

Answer

Attach an Application Load Balancer with cross-zone load balancing enabled so traffic is evenly spread regardless of task location.

Question 14

A media company runs a content management application on EC2 instances in an Auto Scaling group across three Availability Zones. Shared user-uploaded assets are stored on an Amazon EFS file system mounted by all instances. Compliance requires that any accidental deletion or corruption of files can be recovered to a point no more than 1 hour old, and the recovery process must be fully automated and centrally auditable across the company's accounts. Which approach best meets these requirements with the least operational overhead?

Accepted Answer

Enable AWS Backup with a backup plan targeting the EFS file system, set the backup frequency to hourly with continuous backups (point-in-time recovery) enabled, and use a Backup vault with cross-account management via AWS Organizations.

Answer

Write a cron job on one EC2 instance that uses rsync to copy the EFS contents to an S3 bucket every hour, and restore files manually from S3 when needed.

Answer

Enable EFS lifecycle management to transition files to Infrequent Access storage, and rely on the durability of EFS across AZs to protect against deletion.

Answer

Create an hourly EFS-to-EFS replication configuration to a second file system in another Region and fail over to it whenever files are deleted.

Question 15

A financial services company runs a session-store on a self-designed Amazon ElastiCache for Redis (cluster mode disabled) deployment with a single primary node in one Availability Zone. During a recent AZ impairment, the primary became unreachable and the application lost all active user sessions, forcing every user to re-authenticate. The team must minimize both recovery time and data loss for future AZ failures while keeping the change fully managed by AWS. What should the DevOps engineer implement?

Accepted Answer

Enable Multi-AZ with automatic failover by adding one or more read replicas in different Availability Zones to the existing replication group.

Answer

Configure an EventBridge rule on the ElastiCache node-failure event that triggers a Lambda function to create a new primary node from the latest daily backup.

Answer

Schedule daily ElastiCache backups to S3 and write an SSM Automation runbook that restores the snapshot into a new cluster when CloudWatch reports the primary unhealthy.

Answer

Migrate the session data to a single-node Memcached cluster spread across multiple Availability Zones to gain built-in AZ redundancy.

Question 16

A financial services company runs a fleet of EC2 instances with attached EBS volumes storing transactional data. Compliance requires an RPO of 1 hour and that recovery point snapshots be automatically created, retained for 30 days, and copied to a second region for disaster recovery. The DevOps team wants a fully managed, policy-driven solution that requires no custom Lambda code or cron servers to maintain. Which approach best meets these requirements?

Accepted Answer

Create an Amazon Data Lifecycle Manager (DLM) snapshot lifecycle policy targeting the volumes by tag, with a 1-hour schedule, 30-day retention, and cross-region copy enabled to the DR region.

Answer

Write an AWS Lambda function triggered by an EventBridge scheduled rule every hour to call CreateSnapshot and CopySnapshot, and a second function to prune snapshots older than 30 days.

Answer

Enable EBS fast snapshot restore on all volumes and rely on it to maintain hourly recovery points that are automatically replicated to the DR region.

Answer

Configure AWS Backup with a daily backup plan and a lifecycle rule that transitions snapshots to cold storage after 1 hour and copies them cross-region.

Question 17

A company runs a production workload across three Availability Zones in a single VPC. Private subnets in all three AZs currently route outbound internet traffic through a single NAT gateway located in AZ-a, which is used for downloading OS patches and calling external APIs. During a recent AZ-a service disruption, workloads in AZ-b and AZ-c lost all outbound internet connectivity even though their own compute resources remained healthy. The DevOps team must eliminate this cross-AZ dependency with the least ongoing operational effort. What should they do?

Accepted Answer

Deploy one NAT gateway per AZ and configure each private subnet's route table to send 0.0.0.0/0 traffic to the NAT gateway in its own AZ.

Answer

Replace the NAT gateway with a fleet of self-managed NAT instances in an Auto Scaling group spanning all three AZs behind a Network Load Balancer.

Answer

Create a second NAT gateway in AZ-b and configure Route 53 health checks to fail traffic over from the AZ-a NAT gateway when it becomes unavailable.

Answer

Attach an egress-only internet gateway to the VPC and point all private subnet route tables to it for high availability across AZs.

Question 18

A financial services company runs an active-active application across us-east-1 and eu-west-1. Each region has an Application Load Balancer fronting an ECS service. They use Route 53 latency-based routing with health checks pointing at each ALB. During a partial regional degradation, the ECS tasks in eu-west-1 remained running and passed ALB target group health checks, but a critical downstream dependency (a regional payment API) was returning HTTP 500 errors. Route 53 continued sending European users to the failing region. The DevOps team must ensure Route 53 stops routing to a region when the application is functionally unhealthy, even if the ALB and tasks appear healthy. What is the MOST effective solution?

Accepted Answer

Configure the Route 53 health check to query a deep health-check endpoint on the ALB that validates the downstream payment API, and associate a CloudWatch alarm-based failover so unhealthy regions are removed from DNS responses.

Answer

Reduce the ALB target group health check interval and unhealthy threshold so tasks are deregistered faster when the payment API fails.

Answer

Switch Route 53 from latency-based routing to a simple weighted routing policy with equal weights across both regions.

Answer

Enable ECS service auto scaling based on CPU utilization so additional tasks launch in eu-west-1 to absorb the payment API errors.

Question 19

A financial services company runs a critical application in us-east-1 backed by an Amazon RDS for PostgreSQL instance. Compliance requires a documented disaster recovery strategy with an RTO of 30 minutes and an RPO of 5 minutes, while keeping standby costs minimal. The DevOps team wants to automate failover to us-west-2 with the least possible ongoing infrastructure cost that still meets these targets. Which approach BEST satisfies these requirements?

Accepted Answer

Implement a pilot light architecture: maintain a cross-region RDS read replica in us-west-2, keep the application infrastructure defined as CloudFormation templates (not running), and use an automation runbook to promote the replica and deploy the app stack on failover.

Answer

Deploy a full active-active multi-region setup with RDS instances in both regions synchronized via a custom logical replication script and Route 53 weighted routing.

Answer

Rely solely on automated RDS snapshots copied to us-west-2 every 6 hours, and restore a new database and launch infrastructure via CloudFormation only when a disaster is declared.

Answer

Enable Multi-AZ for the RDS instance in us-east-1 and configure an EventBridge rule to trigger a Lambda that redeploys the stack in us-west-2 during a regional outage.

Question 20

A financial services company runs a critical transaction API on an Amazon RDS for PostgreSQL Multi-AZ deployment. During a recent AZ disruption, RDS automatically failed over to the standby instance in about 90 seconds, but the application layer continued to fail for nearly 15 minutes because connections kept resolving to the old, now-unreachable instance IP. The DevOps team must ensure the application recovers automatically within seconds of a future failover, without manual intervention. Which change most directly addresses the root cause?

Accepted Answer

Ensure the application connects through the RDS cluster/instance DNS endpoint and lower the JVM/OS DNS TTL caching so the new IP is picked up quickly after failover.

Answer

Configure the application to connect using the RDS instance's cached IP address and add a retry loop with exponential backoff.

Answer

Enable RDS Multi-Region read replicas and point the application to the closest replica endpoint to reduce failover time.

Answer

Increase the RDS backup retention period and enable Performance Insights to detect the failover faster.

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