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

Question 1

A company uses AlB with target groups for a microservices architecture. They need to ensure that if a target group has no healthy targets, the ALB returns a custom error page instead of a 503. How can this be achieved?

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

Accepted Answer

Enable the ALB's custom error response and specify the error page.. An Application Load Balancer has no built-in 'custom error response' setting that maps specific ALB-generated error codes (like 503 for no healthy targets) to an external custom page -- that capability does not exist on ALB. The ALB's only related native feature is a listener rule 'fixed-response' action, which returns a small static inline body and cannot be triggered specifically by 'no healthy targets in the target group.' To serve a real custom error page when the ALB returns a 503, the standard AWS-documented solution is to place Amazon CloudFront in front of the ALB and configure CloudFront's custom error response feature to map HTTP 503 to a page hosted in S3 (or another origin).

Answer

Configure a Lambda@Edge function to replace the 503 response.

Answer

Use Amazon CloudFront to cache a custom error page.

Answer

Use the ALB's fixed response action to return a custom error page.

Question 2

A company runs a mission-critical database on Amazon RDS for MySQL. They need to ensure that if the primary DB instance fails, the database remains available with minimal downtime. Which TWO configurations should they implement? (Choose TWO.)

Accepted Answer

Create a read replica in the same region.. For a mission-critical MySQL RDS database requiring minimal downtime on primary failure, Multi-AZ deployment (D) is the primary and most direct answer, providing automatic synchronous failover in 60-120 seconds. A same-region read replica (B) is a secondary, complementary safeguard: it cannot auto-failover, but if the primary and its Multi-AZ standby were both to become unavailable, a DBA can manually promote the replica, which is faster than restoring from backup even though it involves data-loss risk from replication lag. Both are legitimate 'reduce downtime' investments, but the deep_dive text should not claim Multi-AZ is the 'only' correct option when B is also credited.

Answer

Enable automated backups with point-in-time recovery.

Answer

Enable deletion protection on the DB instance.

Answer

Configure cross-region replication.

Question 3

A company runs a critical microservices application on Amazon EKS with multiple services. They use an ingress controller (ALB Ingress Controller) to route traffic to services. They notice that when a pod fails, new requests are still sent to the failed pod for a few seconds, causing errors. The health check interval is set to 5 seconds. They want to minimize the time during which failed pods receive traffic. They also need to ensure that during rolling updates, traffic is not sent to pods that are terminating. Which solution should they implement?

Accepted Answer

Configure readiness probes on the pods and set the ALB ingress controller to use the readiness probe endpoint.. The root cause is that the ALB Ingress Controller routes traffic based on readiness, not liveness. Configuring readiness probes on pods and instructing the ALB Ingress Controller to use the readiness probe endpoint ensures that only pods passing readiness checks receive traffic. During rolling updates, terminating pods fail readiness and are removed from the target group before shutdown, eliminating errors.

Answer

Define liveness probes for all pods with a low failure threshold.

Answer

Use pod anti-affinity to spread pods across nodes.

Answer

Decrease the health check interval on the ALB target group to 2 seconds.

Question 4

A company runs a web application on EC2 instances behind an Application Load Balancer (ALB). The application stores session state in an RDS MySQL database. During a recent spike in traffic, the database CPU utilization reached 100%, causing slow responses. To improve resilience, what should a DevOps engineer do?

Accepted Answer

Migrate session state to Amazon ElastiCache for Redis with replication.. Migrating session state to Amazon ElastiCache for Redis with replication is the correct answer because it removes the session read/write load from RDS, provides sub-millisecond latency, and adds a replicated cache layer that survives node failures. Redis supports persistence and replication, making it suitable for session state that must be resilient. This directly addresses the database CPU saturation caused by session churn.

Answer

Migrate session state to Amazon ElastiCache for Memcached.

Answer

Increase the RDS instance size and enable Multi-AZ deployment.

Answer

Configure Auto Scaling groups for the EC2 instances based on CPU utilization.

Question 5

A DevOps team is designing a highly available multi-tier application on AWS. The application runs on EC2 instances in an Auto Scaling group across two Availability Zones. The team uses an Application Load Balancer (ALB) to distribute traffic. The application requires the ALB to be accessible via a single, static IP address for whitelisting by third-party partners. What is the most resilient solution?

Accepted Answer

Use an Application Load Balancer (ALB) with AWS Global Accelerator.. AWS Global Accelerator can be placed directly in front of an existing Application Load Balancer as an endpoint. It provides two static anycast IP addresses as fixed entry points and routes traffic to the ALB across AZs, giving partners static IPs to whitelist without discarding the ALB's Layer 7 features (host/path routing, WebSockets) or re-architecting to an NLB.

Answer

Use a Network Load Balancer (NLB) with a static IP address and Route 53 weighted routing to multiple NLBs.

Answer

Use a Network Load Balancer (NLB) with an Elastic IP per Availability Zone and front it with AWS Global Accelerator.

Answer

Use a Network Load Balancer (NLB) with Elastic IP addresses attached to each subnet in each AZ.

Question 6

A company is running a critical application on Amazon RDS for PostgreSQL with Multi-AZ deployment. The application performs frequent writes. During a recent failover test, the team observed that the application experienced a 30-second write outage. To minimize downtime during automatic failovers, which configuration change should the DevOps engineer implement? (Choose TWO.)

Accepted Answer

Configure Amazon RDS Proxy in front of the RDS instance.. The RDS/Aurora endpoint's DNS record TTL is set and controlled by AWS (fixed at 5 seconds) and is not something a customer can configure to '1 second' or any other value. The complementary client-side action to reduce failover impact is configuring the APPLICATION/CLIENT's DNS cache TTL (e.g., the JVM's networkaddress.cache.ttl, or the OS resolver cache) to a short value like 60 seconds or less, combined with connection retry logic -- not modifying the RDS endpoint's own DNS TTL, which AWS already manages.

Answer

Enable Performance Insights to monitor database load.

Answer

Use synchronous replication to the standby instance.

Answer

Increase the DB instance class to a larger size.

Question 7

A DevOps engineer is designing a disaster recovery (DR) strategy for a stateless web application running on EC2 instances with an Application Load Balancer. The application stores data in Amazon S3 and uses a DynamoDB table for session data. The primary region is us-east-1 and the DR region is us-west-2. The RTO is 15 minutes and RPO is 1 minute. Which strategy is most cost-effective and meets the requirements?

Accepted Answer

Use a warm standby with a minimal environment in the DR region, using DynamoDB Global Tables and S3 CRR, with Auto Scaling to scale up on failover.. A warm standby with a minimal but functional environment in us-west-2, combined with DynamoDB Global Tables (sub-second replication, meeting 1-minute RPO) and S3 Cross-Region Replication, plus Auto Scaling to expand on failover, meets the 15-minute RTO and 1-minute RPO at the lowest cost. Pilot light would be cheaper but requires provisioning time that may exceed 15 minutes, and active-active is more expensive than needed.

Answer

Use a warm standby strategy with a scaled-down but fully functional environment in the DR region.

Answer

Use a multi-site active-active strategy, running the application in both regions with a Route 53 latency-based routing.

Answer

Use a pilot light strategy with CloudFormation templates to provision resources in the DR region on failure.

Question 8

A company runs a containerized application on Amazon ECS with Fargate. The application uses an Application Load Balancer (ALB) and stores data in Amazon Aurora Serverless v2. The application experiences intermittent timeouts during periods of rapid scaling. The DevOps engineer notices that the Aurora database's ACU utilization spikes to 100% during these events. What should the engineer do to improve resilience? (Choose THREE.)

Accepted Answer

Implement exponential backoff and jitter in application retry logic.. Exponential backoff and jitter in retry logic prevent thundering herd during scaling events, reducing load on the database. Option D is correct because configuring Aurora Auto Scaling with a higher maximum ACU allows the database to handle increased traffic bursts, preventing ACU saturation. Option E is correct because Amazon RDS Proxy manages database connections efficiently, reducing connection overhead and improving scalability during rapid scaling. Option A is incorrect because increasing Fargate task memory/CPU does not address the database bottleneck; the issue is database ACU saturation. Option C is incorrect because ElastiCache caches reads, but the issue is likely write-heavy scaling; caching does not alleviate write load.

Answer

Increase the Fargate task memory and CPU limits.

Answer

Add Amazon ElastiCache in front of the database for caching.

Question 9

A company uses AWS CloudFormation to deploy infrastructure. The DevOps team wants to ensure that if a stack update fails, the stack automatically rolls back to the previous known good state. The team also wants to receive notifications of the rollback. Which combination of steps should the team take? (Choose THREE.)

Accepted Answer

Set the 'Rollback on failure' option to 'Yes' in the CloudFormation stack properties.. Setting 'Rollback on failure' to 'Yes' in the CloudFormation stack properties ensures automatic rollback to the last known good state if the update fails. Option C is correct because configuring an SNS topic as a notification target allows the stack to send notifications (e.g., email) about rollback events. Option B is incorrect because termination protection only prevents accidental deletion of the stack; it does not affect rollback behavior or notifications. Option D is incorrect because CloudWatch Logs log groups are used for storing logs, not for notifications or rollback. Option E is incorrect because drift detection identifies manual changes to resources but does not provide rollback or notifications.

Answer

Enable termination protection on the CloudFormation stack.

Answer

Create a CloudWatch Logs log group and subscribe to stack events.

Answer

Enable drift detection on the CloudFormation stack.

Question 10

A DevOps engineer is troubleshooting an issue where an EC2 instance behind an ALB target group is marked as unhealthy. The instance i-0abcd1234efgh5678 is serving traffic but the health check is timing out. The security group for the instance allows inbound HTTP from the ALB's security group. What is the most likely cause?

Accepted Answer

The instance's web server is overloaded and not responding within the health check interval.. A 404 from the health check path would cause the target to be marked unhealthy with the reason code Target.ResponseCodeMismatch, not a timeout-related reason. Real ALB health-check reason codes include Target.Timeout, Target.ResponseCodeMismatch, Target.FailedHealthChecks, Target.NotRegistered, and Elb.InternalError; there is no 'Application.Invalid' reason code in AWS documentation.

Answer

The instance is in a private subnet with no route to the internet.

Answer

The health check path is misconfigured and returns a 404 status code.

Answer

The security group of the ALB does not allow outbound traffic to the instance.

Question 11

A DevOps engineer created this IAM policy for a CI/CD pipeline role. The pipeline needs to stop and start production EC2 instances and manage Auto Scaling groups. However, the pipeline fails when trying to stop an instance. What is the most likely reason?

Accepted Answer

The instance does not have the tag 'Environment' with value 'production'.. The first statement in the policy allows ec2:StartInstances and ec2:StopInstances only if the instance has the tag 'Environment' with value 'production'. Without this tag, the actions are denied. The pipeline fails to stop an instance because the instance likely lacks this tag. Option A (ec2:DescribeInstances) is not required for stop operations and is allowed by the policy. Option B (autoscaling:UpdateAutoScalingGroup) is not related to stopping instances. Option D is incorrect because the ec2:StopInstances permission exists but is conditional on the tag.

Answer

The policy does not allow ec2:DescribeInstances for all instances.

Answer

The policy does not allow autoscaling:UpdateAutoScalingGroup for instances.

Answer

The ec2:StopInstances action requires an additional ec2:DescribeInstanceStatus permission.

Question 12

A DevOps engineer is reviewing a CloudFormation template for an S3 bucket that stores application logs. The bucket has versioning enabled and a lifecycle rule to expire noncurrent versions after 30 days. The bucket policy allows public read access to all objects. The company's security policy requires that all S3 buckets block public access. Which change should the engineer make to comply?

Accepted Answer

Remove the bucket policy statement that grants public access.. The bucket policy currently allows public read access, which violates the security policy requiring all S3 buckets to block public access. To comply, the engineer must remove the bucket policy statement that grants public access or enable the 'Block all public access' setting on the bucket. Option A (changing the bucket name) does not affect public access. Option B (enabling default encryption) enhances security but does not block public access. Option D (removing the lifecycle rule) is unrelated to public access.

Answer

Change the bucket name to include 'private'.

Answer

Enable default encryption on the bucket.

Answer

Remove the lifecycle rule that expires noncurrent versions.

Question 13

A company has a critical application running on Amazon EC2 instances in an Auto Scaling group. The application writes logs to an Amazon EFS file system. The DevOps team needs to ensure that log data is durable and available even if an Availability Zone fails. The EFS file system is currently in one AZ. What should the team do? (Choose TWO.)

Accepted Answer

Enable AWS Backup for the EFS file system with daily backups.. Option B is correct because enabling AWS Backup for the EFS file system with daily backups creates point-in-time recovery copies that are stored durably and can be restored even if the source file system or its Availability Zone is lost, directly addressing the durability requirement. Option D is correct because a Regional (Standard) EFS file system stores data redundantly across multiple Availability Zones in the region, so the log data remains available if a single AZ fails, which is exactly the resilience the DevOps team needs. Option A is incorrect because changing the throughput mode to Provisioned only affects performance/cost, not durability or AZ-failure resilience. Option C is incorrect because a cron job copying logs to S3 is an ad hoc, application-level workaround that does not make the EFS file system itself durable or AZ-resilient and may miss data between runs. Option E is incorrect because mounting an EFS file system from multiple AZs does not help when the file system is created in a single AZ; a One Zone file system is accessible only within its AZ, so multi-AZ mounting cannot provide AZ-failure availability.

Answer

Increase the EFS throughput mode to Provisioned.

Answer

Copy the log files to Amazon S3 using a cron job.

Answer

Configure the EC2 instances to mount the EFS file system from multiple Availability Zones.

Question 14

A company is migrating a monolithic application to a microservices architecture on Amazon EKS. The application uses a relational database. The team wants to ensure that database connections are managed efficiently and that the database can withstand a sudden spike in connections from multiple microservices. Which solution should the DevOps engineer implement? (Choose THREE.)

Accepted Answer

Deploy Amazon RDS Proxy in front of the database.. Option C is correct because Amazon RDS Proxy is a fully managed, highly available database proxy that pools and shares database connections from many microservice pods, which reduces the connection overhead on the underlying RDS database and helps it absorb sudden connection spikes. Option D is correct because raising the database's max_connections parameter allows more concurrent sessions, and enabling storage/compute Auto Scaling (e.g., RDS storage autoscaling and instance scaling) lets the database handle increased load and connection demand during traffic surges. Option E is correct because a connection pool sidecar such as PgBouncer runs alongside each application container in the EKS pod and multiplexes many client connections onto a smaller number of backend PostgreSQL connections, improving connection efficiency and resilience to spikes. Option A is not appropriate because direct connections from every microservice pod multiply connection counts and exhaust database limits, which is exactly the problem being solved. Option B is not appropriate because ElastiCache for Redis caches query results to reduce read latency and database load, but it does not manage or pool database connections and therefore does not address the connection-spike requirement.

Answer

Use direct database connections from each microservice pod.

Answer

Use Amazon ElastiCache for Redis to cache database query results.

Question 15

A company runs a web application on EC2 instances in an Auto Scaling group across three Availability Zones. The application uses an Application Load Balancer (ALB) and stores session data in an ElastiCache for Redis cluster with cluster mode enabled. During a recent deployment, a new version of the application caused a memory leak in the Redis cluster, leading to out-of-memory errors and evictions. The DevOps team wants to prevent future deployments from affecting the Redis cluster's health. What should the team do? (Choose TWO.)

Accepted Answer

Implement a blue/green deployment strategy using a separate Redis cluster for the new version.. Option A is correct because a blue/green deployment with a separate Redis cluster isolates the new application version's memory leak from the production Redis cluster, so any out-of-memory errors or evictions occur only in the green environment and production health is preserved. Option E is correct because CloudWatch provides ElastiCache metrics such as DatabaseMemoryUsagePercentage, BytesUsedForCache, and Evictions; alarms on these metrics can trigger an automatic rollback (for example via CodeDeploy or a Lambda action) before the faulty deployment degrades the production Redis cluster. Option B is not correct because increasing the node type only adds capacity and does not prevent a memory leak from eventually exhausting memory or causing evictions. Option C is not correct because disabling cluster mode reduces sharding and scalability rather than addressing the memory leak, and it may harm performance. Option D is not correct because a manual snapshot only provides a recovery point after damage occurs; it does not prevent the deployment from affecting Redis health.

Answer

Increase the ElastiCache node type to a larger instance size.

Answer

Disable cluster mode on the Redis cluster to reduce overhead.

Answer

Take a manual snapshot of the Redis cluster before each deployment.