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

Question 1

A company uses AWS Lambda for processing events from Amazon S3. Recently, the Lambda function started timing out after the 15-minute limit for some large files. The function downloads the entire file to /tmp before processing. What should a DevOps engineer do to resolve this issue with minimal code changes?

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

Accepted Answer

Use S3 Select to filter and retrieve only necessary data, reducing file size. S3 Select allows you to retrieve only a subset of data from an S3 object by using simple SQL expressions, which drastically reduces the amount of data transferred and processed. Since the Lambda function currently downloads the entire file to /tmp, using S3 Select to filter and retrieve only necessary data reduces the file size and processing time, helping to avoid the 15-minute timeout. This approach requires minimal code changes because you only need to modify the S3 GetObject call to include a SelectObjectContent request, rather than restructuring the entire function logic. Thus, it directly addresses the root cause: excessive data volume causing long download and processing times.

Answer

Switch the Lambda runtime from Python to Node.js for faster execution

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Increase the Lambda function memory to 10,240 MB to improve CPU performance

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Modify the function to read the file in streaming chunks from S3

Question 2

A company runs a critical database on Amazon RDS for PostgreSQL with Multi-AZ deployment. The application experiences a brief outage during automatic failover. To improve availability, the company wants to reduce the failover time. What should they do?

Accepted Answer

Enable Multi-AZ DB cluster with synchronous replication and a standby in a different AZ. Amazon RDS Multi-AZ DB clusters use synchronous replication to a standby in a different AZ and provide faster failover (typically under 35 seconds) compared to the classic Multi-AZ instance deployment, which uses a single standby and can take 60–120 seconds. This directly addresses the requirement to reduce failover time while maintaining high availability. The cluster configuration also offers two readable standbys, improving both availability and read scaling.

Answer

Create a cross-Region Read Replica and promote it during failure

Answer

Increase the DB instance class size to improve I/O performance

Answer

Remove Multi-AZ and use a single instance with increased backup frequency

Question 3

A company runs a containerized microservices architecture on Amazon ECS with Fargate. The services communicate via an internal Application Load Balancer. Recently, a new deployment of Service A caused its health checks to fail. The DevOps engineer notices that the old tasks remain running and the service is unavailable. What configuration change would prevent this issue in future deployments?

Accepted Answer

Set the deployment minimum healthy percent to 50 and maximum percent to 100 with a health check grace period. Setting the deployment minimum healthy percent to 50 and maximum percent to 100, combined with a health check grace period, ensures that ECS keeps at least half the tasks running during deployment and does not kill old tasks until new ones pass health checks. The health check grace period gives new tasks time to start and pass ALB health checks before ECS considers them unhealthy, preventing the old tasks from being terminated prematurely and avoiding service unavailability. This configuration directly prevents the issue described.

Answer

Set the deployment circuit breaker to rollback on deployment failure and disable rollback

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Change the deployment controller from ECS to CodeDeploy for blue/green deployments

Answer

Set the deployment minimum healthy percent to 0 and maximum percent to 200

Question 4

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

Migrate to Amazon EFS and mount the same file system on all instances. Use Amazon EFS and mount the same file system on all instances in the Auto Scaling group. EFS is a durable, multi-AZ, multi-writer network file system, so data written by one instance persists independently of any single instance's lifecycle. When an instance fails and Auto Scaling launches a replacement, the new instance mounts the same EFS file system via a bootstrap script/user data and immediately has access to the existing data, enabling fast resumption without any data loss. EBS Multi-Attach (option D) is not appropriate here because it is limited to a single Availability Zone, only supports io1/io2 volumes on Nitro instances, and requires a cluster-aware file system to prevent data corruption when accessed by multiple instances concurrently -- an unfulfilled prerequisite that would risk the very data loss the company is trying to avoid.

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

Use an EBS Multi-Attach volume attached to all instances in the Auto Scaling group

Question 5

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, so when a failover occurs, the endpoint automatically redirects to the new primary. Using the cluster endpoint requires no code changes and makes the application resilient to failover. The reader endpoint is for read-only traffic and would fail on writes.

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 6

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

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

Question 7

A company is designing a disaster recovery plan for a critical application with an RPO of 15 minutes and RTO of 1 hour. The application runs on EC2 instances with an RDS MySQL database. The primary Region is us-east-1. Which THREE actions should they take to meet the RPO and RTO? (Choose three.)

Accepted Answer

Schedule automated AMI backups of EC2 instances every 15 minutes. Automated AMI backups of EC2 instances every 15 minutes align with the 15-minute RPO by capturing incremental snapshots of the instance volumes. These AMIs can be used to launch replacement EC2 instances in the secondary Region within the 1-hour RTO, provided the infrastructure is pre-staged. The frequency of 15 minutes ensures that data loss is limited to at most 15 minutes of changes.

Answer

Launch EC2 instances in a single Availability Zone in the secondary Region to reduce costs

Answer

Use AWS CloudFormation StackSets to deploy identical infrastructure in the secondary Region

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. Cross-region read replicas asynchronously replicate data from the primary RDS MySQL instance to a replica in a secondary region. During a regional failure, the replica can be promoted to a standalone primary, providing a warm standby for database resilience in an active-active architecture. This is the only AWS-native RDS MySQL option that supports cross-region replication with promotion capability.

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 company is designing a disaster recovery plan for an RDS PostgreSQL database. They have a cross-region read replica. Which THREE steps should they take to ensure a successful failover?

Accepted Answer

Configure applications to use the new database endpoint. Option D is correct because promoting the cross-region read replica to a standalone database instance is the essential action that turns the replica into a writable primary, which is required to complete the failover. Option B is correct because after promotion the instance receives a new endpoint, so applications must be reconfigured to use that new database endpoint to reconnect to the promoted primary. Option C is correct because updating the Route 53 DNS record to point to the new master lets clients resolve the database by a stable DNS name and reach the promoted instance without manual reconfiguration. Option A is not required because automated backups are not a prerequisite for promoting a read replica, and Option E is not required because Multi-AZ is a high-availability feature for a primary instance and is not enabled on a read replica before promotion.

Answer

Enable automated backups on the replica before promotion

Answer

Enable Multi-AZ on the read replica before promotion

Question 10

A company runs a critical web application on EC2 instances behind an Application Load Balancer (ALB) across multiple Availability Zones. During a recent failure of one AZ, the application experienced downtime because the Auto Scaling group did not launch new instances quickly enough. What should a DevOps engineer do to improve resilience?

Accepted Answer

Configure the Auto Scaling group to span multiple AZs and enable health checks to replace unhealthy instances.. Configuring the Auto Scaling group to span multiple Availability Zones (AZs) and enabling health checks ensures that if an entire AZ fails, the Auto Scaling group can launch replacement instances in the remaining healthy AZs. The ALB health checks detect unhealthy instances and trigger the Auto Scaling group to replace them, reducing downtime. This approach leverages the fault isolation of multiple AZs and the automatic scaling capabilities of AWS Auto Scaling.

Answer

Use a larger AMI to reduce boot times.

Answer

Increase the instance size of the EC2 instances to handle more traffic.

Answer

Configure the Auto Scaling group to launch instances in a single AZ with a larger instance count.

Question 11

A company runs a containerized application on Amazon EKS. The application uses an ALB Ingress Controller. During a cluster upgrade, the ingress controller stops responding, causing downtime. The team wants to ensure resilience during upgrades. Which approach is BEST?

Accepted Answer

Schedule the ingress controller pod on a dedicated node with a taint that prevents node upgrades.. Applying a taint (e.g., `node-role.kubernetes.io/ingress:NoSchedule`) to a dedicated node and scheduling the ingress controller pod with a corresponding toleration ensures that the pod is not evicted during node upgrades. Managed node groups or cluster upgrades typically cordon and drain nodes, but a tainted node can be excluded from the upgrade process by setting `maxUnavailable: 0` or using a node group with `updateConfig` to skip that node. This prevents the ALB Ingress Controller from becoming unavailable during the cluster upgrade.

Answer

Use a horizontal pod autoscaler for the ingress controller.

Answer

Enable cluster autoscaler to add more nodes during the upgrade.

Answer

Use a managed node group with a higher instance count.

Question 12

A company is designing a resilient storage solution for a critical application. The data must be highly available and durable. Which TWO services meet these requirements? (Choose TWO.)

Accepted Answer

Amazon EFS. Amazon EFS (A) is correct because it is a fully managed, multi-AZ elastic file system that replicates data across Availability Zones within a Region, providing high availability and durability for concurrent access from multiple EC2 instances. Amazon S3 (D) is correct because it is designed for 99.999999999% (11 nines) durability and 99.99% availability by automatically storing objects redundantly across multiple devices and Availability Zones. Amazon EBS with RAID 1 (B) is not correct because EBS volumes are tied to a single Availability Zone, so RAID 1 mirroring does not protect against an AZ failure. Amazon S3 Glacier Deep Archive (C) is not correct because it is an archival storage class with retrieval times of 12 hours, making it unsuitable for a critical, highly available application. Amazon EC2 instance store (E) is not correct because it is ephemeral, non-persistent local storage that is lost if the instance stops or the host fails, offering no durability guarantee.

Answer

Amazon EBS with RAID 1

Answer

Amazon S3 Glacier Deep Archive

Answer

Amazon EC2 instance store

Question 13

A company runs a stateful web application on EC2 instances behind an ALB. The application uses sticky sessions (session affinity) to maintain user sessions. During a deployment, the company wants to update the application with zero downtime and ensure that in-flight sessions are not lost. Which deployment strategy should they use?

Accepted Answer

Use a blue/green deployment: launch a new Auto Scaling group, register it with a new target group, and gradually shift traffic using weighted target groups on the ALB.. A blue/green deployment with weighted target groups on the ALB allows the company to launch the new application version in a separate Auto Scaling group, register it with a new target group, and then gradually shift traffic using ALB weighted target group rules. Because the ALB uses sticky sessions (session affinity), existing users continue to be routed to the same backend instance during the gradual shift, preserving in-flight sessions while new sessions can be directed to the new environment. This provides zero-downtime deployment with the ability to roll back instantly by shifting weights back if issues arise.

Answer

Perform a rolling update of the Auto Scaling group with a health check grace period.

Answer

Use an immutable deployment by launching a new Auto Scaling group and then updating the ALB target group to point to the new group.

Answer

Use a canary deployment with AWS Lambda to gradually route a percentage of requests to the new version.

Question 14

A company has a production RDS for PostgreSQL database. They need to perform a major version upgrade with minimal downtime. Which strategy provides the LEAST downtime while maintaining data integrity?

Accepted Answer

Use the AWS Database Migration Service (DMS) to continuously replicate data to a new database with the new version.. DMS with continuous (CDC) replication lets you perform an initial full load to a new PostgreSQL instance on the target engine version and then keep it in sync with ongoing changes, so the only downtime is the brief cutover once replication lag reaches zero. This is the correct choice specifically because a same-version RDS read replica cannot be created on a different PostgreSQL major version (physical streaming replication requires matching major versions), a snapshot restore requires a full stop-the-world backup/restore window, and modifying the instance in place triggers a lengthy reboot-based outage. DMS's need to separately migrate non-table objects (stored procedures, triggers, sequences) is a real operational cost but does not change the fact that it offers the least downtime of the four options.

Answer

Take a snapshot of the database and restore it as a new database with the new engine version.

Answer

Create a read replica with the new engine version, promote it to a standalone database, and update the application connection string.

Answer

Modify the existing DB instance and set the engine version to the new version.

Question 15

A company runs a web application on EC2 instances behind an ALB. To improve resilience, they want to automatically re-register failed instances. Which solution meets this requirement?

Accepted Answer

Enable EC2 instance recovery and configure ALB health checks to deregister unhealthy instances.. Enabling EC2 instance recovery automatically restarts the instance on a new healthy host if the underlying hardware fails, while ALB health checks detect application-level failures and deregister unhealthy instances from the target group. This combination ensures failed instances are automatically replaced in the load balancer's rotation without manual intervention, meeting the resilience requirement.

Answer

Set up a CloudWatch alarm to terminate the instance and notify an operator to re-register it.

Answer

Configure Auto Scaling to launch a new instance on instance failure.

Answer

Use Route 53 health checks to detect failure and update DNS to remove the instance.