DOP-C02 Resilient Cloud Solutions Practice Test 3 — 15 Questions

Question 1

A company runs a web application on EC2 instances behind an Application Load Balancer. The application experiences intermittent failures due to a single Availability Zone failing. Which solution is MOST resilient and cost-effective?

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

Accepted Answer

Deploy EC2 instances across two Availability Zones and configure the ALB to distribute traffic. Most resilient and cost-effective. Deploying EC2 instances across two Availability Zones and configuring the ALB to distribute traffic ensures high availability by handling a single AZ failure without over-provisioning. Option A is wrong because using a larger instance in the same AZ does not address AZ failure. Option B is wrong because using three AZs with a single instance each and a Network Load Balancer is more expensive and not necessary for this scenario; ALB already supports cross-zone load balancing. Option C is wrong because migrating to a different region adds latency, complexity, and cost.

Answer

Use a larger instance type in the same Availability Zone

Answer

Use an Auto Scaling group with a single instance in each of three Availability Zones and a Network Load Balancer

Answer

Migrate to a single larger instance in a different region

Question 2

A DevOps engineer is designing a multi-Region active-active architecture for a stateless web application using Route 53 latency-based routing and DynamoDB global tables. The application must continue to serve traffic even if an entire AWS Region becomes unavailable. Which additional step is MOST critical for resilience?

Accepted Answer

Configure Route 53 health checks and associate them with the latency records. Route 53 latency-based routing must be paired with health checks to detect regional failures and automatically route traffic away from unhealthy endpoints. Without health checks, Route 53 continues to route traffic to a failed region. Option A is incorrect because a scheduled scaling policy only handles predictable load patterns, not regional outages. Option B is incorrect because DynamoDB Accelerator (DAX) is an in-memory cache that improves read performance but does not provide failover capability. Option C is incorrect because CloudFront distributes content globally but does not replace the need for Route 53 health checks to manage regional failover for the web application's origin.

Answer

Use an Auto Scaling group with a scheduled scaling policy

Answer

Enable DynamoDB Accelerator (DAX) in each Region

Answer

Place a CloudFront distribution in front of the application

Question 3

A company uses AWS CloudFormation to deploy a multi-tier application. The stack includes an RDS DB instance with Multi-AZ enabled. The database experiences a failover during maintenance. The application reports connection errors for several minutes. What is the MOST likely cause and solution?

Accepted Answer

The application does not implement connection retry logic; implement exponential backoff and retry. The application experiences connection errors during an RDS Multi-AZ failover because it does not implement connection retry logic. The failover typically completes within 60 seconds, but any active connections are dropped. Without retry logic, the application fails to reconnect. Implementing exponential backoff and retry allows the application to handle transient failures. Option A is wrong because there is no configurable Multi-AZ timeout; failover time is not adjustable. Option B is wrong because Multi-AZ uses a standby instance, not a read replica; read replicas are for read scaling. Option C is wrong because an RDS proxy does not eliminate the need for retry logic; misconfiguration is not the primary issue.

Answer

The RDS failover took longer than expected; increase the Multi-AZ timeout

Answer

The read replica was promoted incorrectly; recreate the read replica

Answer

The RDS proxy is misconfigured; disable the proxy for Multi-AZ

Question 4

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 processing jobs and natively supports a retry strategy to automatically retry failed jobs up to a specified number of attempts. It can run on ECS Fargate and manage job queues. Option B (Step Functions) can also retry but requires explicit state machine configuration and is overkill for simple batch retry. Option C (ECS service) does not provide retry logic for tasks; it replaces failed tasks but does not retry on failure. Option D (Lambda) has a 15-minute execution limit, which is insufficient for a job that may take up to 2 hours.

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 5

A company uses an NLB to distribute traffic to a fleet of EC2 instances in a single Availability Zone. During a recent AWS outage in that zone, the application became completely unavailable. The company wants to achieve high availability without rearchitecting the application. Which change is MOST appropriate?

Accepted Answer

Launch EC2 instances in a second Availability Zone and register them with the NLB target group. Registering EC2 instances in a second Availability Zone with the NLB target group allows NLB to route traffic to healthy instances across zones, providing high availability during a zone outage. Option A is incorrect because using a larger instance type and enabling detailed CloudWatch monitoring does not add redundancy across zones. Option B is incorrect because replacing NLB with an ALB still requires multi-AZ configuration to achieve high availability; cross-zone load balancing is already available on NLB. Option C is incorrect because scheduled scaling does not protect against zone failures; it only adjusts capacity predictably.

Answer

Use a larger instance type and enable detailed CloudWatch monitoring

Answer

Replace the NLB with an Application Load Balancer and enable cross-zone load balancing

Answer

Create an Auto Scaling group with a scheduled scaling policy to add instances during peak hours

Question 6

A company runs a containerized application on Amazon ECS with Fargate. The application needs to store session state. Which service provides the MOST resilient and scalable solution?

Accepted Answer

Amazon ElastiCache for Redis. Amazon ElastiCache for Redis provides a highly available, scalable, and low-latency in-memory data store ideal for session state management in a containerized environment. It supports replication and automatic failover, ensuring resilience. Option B (Amazon EFS) is a file storage service with higher latency and not designed for sub-millisecond session retrieval. Option C (ephemeral storage on the container instance) is not durable; data is lost when the container stops or fails. Option D (Amazon S3) is object storage with higher latency and not optimized for frequent read/write operations required for session state.

Answer

Amazon EFS

Answer

Ephemeral storage on the container instance

Answer

Amazon S3

Question 7

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. AWS CodePipeline allows you to configure automatic retries for individual actions by setting a retry count (up to 3) in the pipeline definition. This retries the specific deploy action if it fails due to a transient error, without rerunning the entire pipeline. Option A is wrong because using AWS Step Functions for retry logic adds unnecessary complexity and cost; CodePipeline's built-in retry mechanism is simpler and sufficient for this case. Option C is wrong because AWS CloudFormation does not offer a built-in retry policy at the stack level; the retry must be handled by the orchestrating service (CodePipeline). Option D is wrong because retrying the entire pipeline execution on failure would cause all preceding actions to re-run, which is inefficient and not the intended solution for transient resource limit errors in a single deploy action.

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 8

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 regional, shared file system that can be mounted by EC2 instances across multiple Availability Zones. This ensures that cache data persists independently of instance lifecycle, so if an instance fails, a replacement instance can mount the same EFS file system and access the cached data without loss. Option A is incorrect because an EBS volume can only be attached to one instance at a time (except with Multi-Attach, which is limited to the same AZ) and is tied to a specific Availability Zone, making it unsuitable for an Auto Scaling group spanning two AZs. Additionally, automatically attaching a specific existing volume to new instances is not a standard Auto Scaling feature. Option B is incorrect because periodic snapshots are not real-time; data written between snapshots would be lost, and creating a new volume from a snapshot does not provide continuous access to the latest cache. Option C is incorrect because EBS Multi-Attach volumes can only be attached to instances within the same Availability Zone, so they cannot serve instances in both AZs of the Auto Scaling group.

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 9

A company wants to ensure that its application running on AWS can withstand the failure of an entire AWS Region. Which TWO strategies should the company implement?

Accepted Answer

Deploy the application in multiple AWS Regions using an active-active or active-passive pattern. To withstand an entire AWS Region failure, the company should deploy the application in multiple AWS Regions (A) and replicate data across Regions (C). Deploying across multiple Availability Zones (B) protects only within a single Region. A single CloudFront distribution with multiple origins in the same Region (D) does not provide regional failover. RDS read replicas in the same Region (E) are for read scaling, not disaster recovery across Regions.

Answer

Deploy the application across multiple Availability Zones in a single Region

Answer

Use a single CloudFront distribution with multiple origins in the same Region

Answer

Configure RDS read replicas in the same Region

Question 10

A company runs a stateful web application on EC2 instances behind an ALB. The application stores session data in memory. The company wants to make the application stateless to improve resilience. Which TWO changes should the company make?

Accepted Answer

Disable sticky sessions on the ALB. To make the application stateless, the company should disable sticky sessions on the ALB (option B) and store session data in Amazon ElastiCache for Redis (option D). Disabling sticky sessions ensures that requests can be routed to any instance, and storing session data externally removes the dependency on in-memory state on individual instances, improving resilience. Option A is incorrect because increasing instance memory does not solve the statefulness issue. Option C is incorrect because enabling sticky sessions would maintain state on instances. Option E is incorrect because using an NLB does not address session state management.

Answer

Increase the instance memory to store more sessions

Answer

Enable sticky sessions (session affinity) on the ALB

Answer

Use an NLB instead of an ALB

Question 11

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. C and D are correct. A cross-Region read replica of the RDS instance in the secondary Region provides near-real-time replication, achieving an RPO of less than 1 minute. When a disaster occurs, the read replica can be promoted to a primary instance quickly, meeting the RTO of less than 15 minutes. An AWS Lambda function can automate the promotion process, reducing manual intervention and further improving RTO. Option E is incorrect because automated backups with cross-Region copy are taken periodically (e.g., daily), not continuously, so they cannot achieve an RPO of less than 1 minute.

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

Question 12

A company runs a production web application on EC2 instances behind an Application Load Balancer. The application experiences intermittent high latency. The operations team needs to identify the root cause without affecting live traffic. Which approach is the MOST efficient?

Accepted Answer

Enable detailed CloudWatch metrics on the ALB and analyze ALB access logs. Enabling detailed CloudWatch metrics on the ALB and analyzing ALB access logs provides visibility into request latency patterns without affecting live traffic. Option A is wrong because setting up a separate test environment does not directly help diagnose the current intermittent issue. Option B is wrong because SSHing into instances and running commands can impact production performance and does not provide historical latency data. Option D is wrong because tcpdump generates large packet captures that can degrade performance and requires significant analysis effort.

Answer

Deploy a separate test environment with identical configuration and run load tests

Answer

Enable EC2 detailed monitoring and SSH into each instance to run top and iostat

Answer

Run tcpdump on all EC2 instances and analyze packet captures

Question 13

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?

Accepted Answer

Use S3 Select to filter and retrieve only necessary data, reducing file size. S3 Select allows querying only the necessary data from S3, reducing the amount of data the Lambda function must download and process. This directly addresses the timeout issue by minimizing the data handled, requiring no major architectural changes. Option B is wrong because switching to Node.js does not remove the 15-minute Lambda timeout. Option C is wrong because increasing memory does not extend the maximum execution time. Option D is wrong because streaming the file does not by itself reduce the total data to process; it only might start processing earlier, but the total processing time still may exceed the timeout.

Answer

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

Answer

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

Answer

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

Question 14

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. A Multi-AZ DB cluster with synchronous replication and a standby in a different AZ provides faster failover times compared to standard Multi-AZ, as it includes a reader endpoint and minimizes downtime. Option A is incorrect because cross-Region Read Replicas are for disaster recovery and read scaling, not automatic failover, and promotion takes time. Option C is incorrect because increasing instance size improves performance but does not reduce failover time. Option D is incorrect because removing Multi-AZ would increase downtime during failover.

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 15

A company uses AWS CodeDeploy for blue/green deployments to an Auto Scaling group. The deployment fails because the new instances do not pass health checks. The DevOps engineer discovers that the health check URL returns a 503 error. What is the MOST likely cause?

Accepted Answer

The target group health check path is '/health' but the application does not serve that endpoint. The health check URL returning a 503 error indicates that the application is not responding to the health check endpoint. Since the target group health check path is configured as '/health' but the application does not serve that endpoint, the ALB considers the instances unhealthy, causing CodeDeploy to fail the deployment. This is the most direct cause because the health check is failing at the application layer, not due to infrastructure issues.

Answer

The CodeDeploy agent on the new instances is not running

Answer

The security group for the ALB does not allow inbound traffic on port 80

Answer

The Auto Scaling group health check type is set to EC2 instead of ELB