DOP-C02 Resilient Cloud Solutions Practice Test 10 — 15 Questions

Question 1

A company runs an application on EC2 with a shared Elastic IP. The instance fails and an engineer manually attaches the Elastic IP to a standby instance. To automate this failover, which service should be used?

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

Accepted Answer

CloudWatch Events with a Lambda target. C is correct because CloudWatch Events (now Amazon EventBridge) can detect the EC2 instance state change (e.g., 'stopped' or 'failed') and trigger a Lambda function. The Lambda function can then programmatically disassociate the Elastic IP from the failed instance and reassociate it to a standby instance using the AWS SDK (e.g., ec2.disassociate_address and ec2.associate_address). This provides a fully automated, event-driven failover without manual intervention.

Answer

Use an Auto Scaling group with a lifecycle hook

Answer

AWS Elastic Beanstalk

Answer

Configure a second Elastic IP

Question 2

A company wants to protect its S3 bucket data from accidental deletion or overwrite. Which feature should be enabled?

Accepted Answer

Enable S3 Versioning. S3 Versioning preserves every prior version of an object, so an accidental overwrite creates a new version while the original remains recoverable, and an accidental delete inserts a delete marker rather than removing data. This directly satisfies the requirement to protect against both accidental deletion and overwrite without blocking legitimate writes. Versioning is the foundational control that MFA Delete and replication build upon.

Answer

Enable cross-region replication

Answer

Apply a bucket policy that denies DeleteObject

Answer

Enable MFA Delete

Question 3

A company has a multi-region application with an RDS for MySQL database in us-east-1. They want to minimize downtime if the primary region fails. They set up a cross-region read replica in us-west-2. What additional step is needed for automated failover?

Accepted Answer

Use a custom automation to monitor the primary and promote the replica. B is correct because RDS cross-region read replicas do not support automatic failover; you must use custom automation (e.g., AWS Lambda, Amazon Route 53 health checks, or a custom script) to detect primary region failure and promote the read replica to a standalone instance. This promotion breaks the replication link and makes the replica a writable primary, enabling failover.

Answer

Create a second read replica in the secondary region

Answer

Configure automatic backup retention on the replica

Answer

Enable Multi-AZ on the read replica

Question 4

A company is designing a disaster recovery strategy for a critical application. They need a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 1 minute. Which AWS database service configuration meets these requirements?

Accepted Answer

Aurora Global Database. Aurora Global Database provides a fully managed cross-region disaster recovery solution with typical RPO of 1 second and RTO of 1 minute for regional failover, which meets the required RTO of 15 minutes and RPO of 1 minute. It uses storage-level replication that is asynchronous but very low-latency, and failover can be promoted to the secondary region in under a minute.

Answer

RDS MySQL with Multi-AZ and cross-region read replica

Answer

DynamoDB global tables

Answer

RDS PostgreSQL with cross-region read replica

Question 5

A company uses an Application Load Balancer (ALB) to distribute traffic to EC2 instances. The ALB is in us-east-1a and us-east-1b. They want to ensure that if one AZ fails, traffic is routed only to healthy instances in the other AZ. What configuration is necessary?

Accepted Answer

Enable cross-zone load balancing on the ALB. Cross-zone load balancing must be enabled on the ALB so that traffic can be distributed across instances in all AZs. By default, an ALB routes requests only to targets in the same Availability Zone as the requesting client. Enabling cross-zone load balancing allows the ALB to distribute traffic evenly across all registered targets in all enabled AZs, ensuring that if one AZ fails, traffic can be routed to healthy instances in other AZs. Option B is incorrect because health checks are already enabled by default and do not affect cross-AZ routing. Option C is incorrect because adding more AZs does not change the default AZ-affinity behavior; cross-zone load balancing must be explicitly enabled to utilize multiple AZs for failover.

Answer

Enable sticky sessions (session affinity)

Answer

Configure health checks on the target group

Answer

Add more subnets in additional AZs

Question 6

A company is designing a highly available architecture for a stateless web application using AWS services. Which TWO steps should they take to achieve high availability?

Accepted Answer

Deploy EC2 instances in multiple Availability Zones. Option B is correct because deploying EC2 instances across multiple Availability Zones ensures the application survives an AZ-level failure, which is a fundamental requirement for high availability in AWS. Option E is correct because an Application Load Balancer distributes incoming traffic across healthy targets in multiple AZs, performs health checks, and automatically routes around failed instances, directly supporting high availability for a stateless web tier. Option A is incorrect because storing session state on an EBS volume tied to a single instance creates a single point of failure and is unnecessary for a stateless application. Option C is incorrect because a single NAT instance is itself a single point of failure and cannot provide high availability. Option D is incorrect because choosing a specific instance type like M5 improves performance but does nothing to increase availability.

Answer

Store session state in an EBS volume attached to each instance

Answer

Use a single NAT instance in a public subnet

Answer

Use only M5 instance types for better performance

Question 7

A company uses DynamoDB global tables for a multi-region application. They notice that write conflicts are occurring. Which TWO strategies can reduce write conflicts?

Accepted Answer

Use conditional writes in the application code. Conditional writes prevent overwriting data unless a specified condition is met, thereby reducing write conflicts by ensuring that updates are only applied when the data is in a known state. Application-level conflict resolution allows the application to handle conflicts when they occur, using custom logic to merge or resolve differences, which reduces the impact of conflicts on the database. Option D (increasing write capacity) does not reduce conflicts; it only increases throughput capacity. Option A (reducing read capacity) is unrelated to write conflicts. Option B (DynamoDB Streams with last writer wins) is the default behavior and does not reduce conflicts; it may cause data loss.

Answer

Reduce read capacity units to limit concurrent reads

Answer

Enable DynamoDB Streams with last writer wins

Answer

Increase write capacity units on the table

Question 8

An application running on Amazon ECS with Fargate experiences intermittent failures. The task definition includes a single container with a health check command. Despite the health check passing, the application occasionally returns HTTP 500 errors. The application logs are sent to CloudWatch Logs. What is the MOST likely root cause?

Accepted Answer

The health check command only checks the process status, not the application's ability to serve requests.. A health check command in an ECS task definition typically checks the container process status (e.g., via a shell command or a simple TCP check), not the application's HTTP layer. If the health check passes but the application returns HTTP 500 errors, it indicates the container is running but the application logic is failing (e.g., unhandled exceptions, database connection issues). This mismatch between process-level health and application-level health is a common cause of intermittent failures in containerized applications.

Answer

The application is missing environment variables that are required for certain requests.

Answer

The ECS service is configured with a target tracking scaling policy that reacts too slowly.

Answer

The container port and host port in the task definition do not match the ALB target group port.

Question 9

A company wants to ensure its data in Amazon S3 is protected against accidental deletion. The bucket stores critical documents. Which approach provides the HIGHEST level of resilience?

Accepted Answer

Enable versioning and MFA delete on the bucket.. Enabling versioning and MFA delete provides protection against both accidental overwrites and malicious deletions. Versioning allows recovery of deleted or overwritten objects, while MFA delete adds an extra layer of security by requiring multi-factor authentication for permanent deletions. Option A is incorrect because a bucket policy that denies s3:DeleteObject can prevent deletions but does not allow recovery if the policy is bypassed or changed. Option B is incorrect because lifecycle policies archive objects to Glacier, which reduces costs but does not prevent or recover from accidental deletion. Option D is incorrect because cross-region replication protects against regional failures but does not protect against accidental deletion within the source bucket.

Answer

Apply a bucket policy that denies s3:DeleteObject for all users.

Answer

Enable S3 lifecycle policies to archive objects to Glacier.

Answer

Configure cross-region replication (CRR) to another bucket.

Question 10

A DevOps team uses AWS CodePipeline to deploy a web application. The pipeline has a deploy stage that uses CodeDeploy to deploy to an Auto Scaling group. During deployment, the new instances fail health checks and the deployment rolls back. However, the rollback also fails because the old instances have been terminated. What should the team do to avoid this issue?

Accepted Answer

Use a blue/green deployment strategy in CodeDeploy to keep the old instances running until the new ones pass health checks.. A blue/green deployment strategy in CodeDeploy keeps the old (blue) instances running while the new (green) instances are provisioned and validated, so if the new instances fail health checks, the deployment can roll back to the still-running old instances. This avoids the scenario where in-place deployment terminates old instances before new ones are confirmed healthy, leaving nothing to roll back to. Blue/green also supports traffic shifting controls like all-at-once, linear, or canary.

Answer

Increase the health check grace period in the Auto Scaling group.

Answer

Add a manual approval step before the deploy stage.

Answer

Configure the pipeline to deploy to a new Auto Scaling group each time.

Question 11

A company runs a stateful application on EC2 instances with instance store volumes. The application requires low-latency access to data. The operations team needs to ensure that instance failure does not result in data loss. Which solution is MOST resilient?

Accepted Answer

Replicate data in real time to an EBS volume and take periodic snapshots.. It combines the low-latency performance of instance store volumes with the durability of EBS snapshots. By replicating data in real time to an EBS volume, the application benefits from the instance store's speed while the EBS volume provides a persistent copy that survives instance failure. Periodic snapshots of the EBS volume add further resilience by enabling point-in-time recovery, ensuring data is not lost even if the instance or its instance store fails.

Answer

Use instance store volumes with RAID 1 across multiple instances.

Answer

Use larger instance types with more instance store capacity.

Answer

Create an AMI of the instance periodically to capture the data.

Question 12

A company is using Amazon RDS for MySQL with Multi-AZ deployment. During a recent failover, the application experienced a brief downtime because the DNS cache on the application servers still pointed to the old primary. How can a DevOps engineer minimize this downtime?

Accepted Answer

Use an RDS Proxy to manage connections and reduce DNS dependency.. RDS Proxy acts as a connection broker that maintains persistent connections to the database and abstracts the underlying DNS changes during failover. When a failover occurs, RDS Proxy automatically reconnects to the new primary without requiring the application to resolve a new DNS record, thereby eliminating the downtime caused by stale DNS caches. This reduces the application's dependency on DNS resolution and provides faster failover recovery.

Answer

Configure the application to use the Multi-AZ endpoint instead of the primary endpoint.

Answer

Configure application servers to use a hardcoded IP address instead of the RDS endpoint.

Answer

Increase the TTL on the RDS DNS record.

Question 13

A company uses AWS Lambda to process messages from an Amazon SQS queue. The Lambda function occasionally times out after 15 seconds. To improve resilience, the team wants to ensure messages are not lost and are retried. Which configuration is MOST appropriate?

Accepted Answer

Increase the Lambda timeout to 30 seconds and configure a dead-letter queue (DLQ) for the SQS queue.. Increasing the Lambda timeout to 30 seconds accommodates the occasional processing delays that cause the current 15-second timeout, preventing premature failures. Configuring a dead-letter queue (DLQ) for the SQS queue ensures that messages that repeatedly fail after all retries are exhausted are preserved for analysis and manual reprocessing, rather than being lost. This combination directly addresses the requirement to not lose messages and to allow retries, as Lambda will automatically retry failed invocations up to the function's configured retry count (default 2) before sending the message to the DLQ.

Answer

Reduce the Lambda timeout to 5 seconds to fail fast and retry quickly.

Answer

Set the SQS queue visibility timeout to less than the Lambda timeout.

Answer

Increase the batch size and remove the DLQ to speed up processing.

Question 14

A company uses Amazon CloudFront to distribute content from an S3 bucket origin. Some users report intermittent access errors. The DevOps team suspects the origin is overwhelmed. What is the MOST effective way to improve resilience?

Accepted Answer

Configure CloudFront to perform health checks on the origin.. Configuring CloudFront to perform health checks on the origin allows it to detect origin issues and trigger failover to a secondary origin, improving resilience. CloudFront origin groups support failover based on error rates, effectively acting as health checks. Option A is incorrect because an ALB is not required for origin failover; CloudFront can directly use multiple S3 buckets as origins. Option B (reducing TTL) increases requests to the origin, worsening the problem. Option C (increasing TTL) reduces load but does not address origin failures or provide failover.

Answer

Set up an origin failover with two S3 buckets behind an Application Load Balancer (ALB).

Answer

Reduce the CloudFront cache TTL to serve fresher content.

Answer

Increase the CloudFront cache TTL to reduce requests to the origin.

Question 15

A company is designing a disaster recovery (DR) strategy for a critical application that runs on EC2 instances with an RDS database. The DR site must be in a different AWS Region. The Recovery Point Objective (RPO) is 15 minutes, and Recovery Time Objective (RTO) is 1 hour. Which TWO actions should the company take to meet these objectives? (Choose TWO.)

Accepted Answer

Configure Amazon Route 53 with health checks and failover routing to the DR region.. Options C and D are correct. D: Creating an RDS cross-Region read replica in the DR region allows the replica to be promoted to the primary database with minimal data loss, meeting the 15-minute RPO. C: Configuring Amazon Route 53 with health checks and failover routing enables automatic traffic redirection to the DR region within the 1-hour RTO. Option A is wrong because copying AMIs and RDS snapshots every 15 minutes would require launching EC2 instances and restoring the database from snapshots, which can exceed the 1-hour RTO. Option B is wrong because manually pre-provisioning resources with CloudFormation does not provide the automated failover needed to meet the RTO. Option E is wrong because S3 cross-Region replication does not address the EC2 and RDS components of the application.

Answer

Use AWS Backup to copy EC2 AMIs and RDS snapshots to the DR region every 15 minutes.

Answer

Use AWS CloudFormation to pre-provision resources in the DR region manually.

Answer

Configure S3 cross-Region replication for application data stored in S3.