DOP-C02 Resilient Cloud Solutions Practice Test 5 — 15 Questions

Question 1

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. Deploying EC2 instances across multiple Availability Zones (B) ensures that the application remains available even if one AZ fails. Using an Application Load Balancer (E) distributes incoming traffic across these instances and performs health checks, automatically routing traffic away from unhealthy instances. Option A is incorrect because storing session state on an EBS volume attached to each instance tightly couples state to a single instance, making it unavailable if the instance fails; instead, use a shared session store like ElastiCache or DynamoDB. Option C is incorrect because a single NAT instance is a single point of failure; for high availability, use a NAT Gateway or deploy NAT instances across multiple AZs. Option D is incorrect because instance type selection (M5) does not contribute to high availability; availability is achieved through architectural redundancy, not hardware specifications.

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 2

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 3

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. To failover a cross-region read replica, promote it to a standalone database instance (Option D). After promotion, update the Route 53 DNS record to point to the new master (Option C) and configure applications to use the new database endpoint (Option B). Option A is incorrect because automated backups are enabled by default on the replica once promoted or can be enabled separately, but they are not required prior to promotion. Option E is incorrect because Multi-AZ is not supported on read replicas in the same region; cross-region replicas also cannot have Multi-AZ before promotion. Multi-AZ can be configured after promotion if desired.

Answer

Enable automated backups on the replica before promotion

Answer

Enable Multi-AZ on the read replica before promotion

Question 4

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 5

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 6

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 instances running until the new instances pass health checks, preventing the rollback failure due to terminated instances. Option A is incorrect: increasing the health check grace period only delays health checks but does not solve the root cause of unhealthy instances. Option B is incorrect: a manual approval step before deployment does not affect the rollback mechanism. Option C is incorrect: deploying to a new Auto Scaling group does not inherently keep old instances alive; without blue/green, the old instances would still be terminated during the deployment.

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 7

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 8

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 9

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 10

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 11

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 12

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.

Question 13

A company runs a microservices architecture on Amazon ECS with Fargate. Services communicate via an internal Application Load Balancer (ALB). The operations team notices that occasional traffic spikes cause increased latency and timeouts. The team wants to improve resilience without over-provisioning. Which THREE steps should be taken? (Choose THREE.)

Accepted Answer

Enable ECS Service Connect for inter-service communication to manage traffic distribution.. B is correct because ECS Service Connect provides built-in traffic management for inter-service communication, including load balancing, retries, and circuit breaking. This helps distribute traffic more evenly during spikes, reducing latency and timeouts without requiring over-provisioning.

Answer

Increase the CPU and memory limits in the task definitions.

Answer

Use EC2 launch type with Spot Instances to reduce cost.

Question 14

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 EBS with RAID 1. Amazon S3 (Option D) provides 99.999999999% durability and 99.99% availability by automatically replicating data across multiple Availability Zones (AZs) within a region, making it ideal for highly available and durable storage. Amazon EBS with RAID 1 (Option B) mirrors data across two EBS volumes in the same AZ, offering enhanced durability and availability compared to a single volume, though it remains AZ-bound. Both services meet the requirements for a resilient storage solution.

Answer

Amazon EFS

Answer

Amazon S3 Glacier Deep Archive

Answer

Amazon EC2 instance store

Question 15

A company runs a critical web application on AWS using an Application Load Balancer (ALB) in front of an Auto Scaling group of EC2 instances. The application experiences periodic traffic spikes. To handle these spikes, the company wants to use a combination of proactive scaling based on a predictable schedule and reactive scaling based on CPU utilization. What is the MOST resilient scaling strategy?

Accepted Answer

Use a scheduled scaling policy for the predictable spikes and a step scaling policy for CPU utilization.. It combines scheduled scaling for predictable traffic spikes with step scaling for reactive adjustments based on CPU utilization, providing both proactive and reactive resilience. Scheduled scaling adjusts capacity in advance of known events, while step scaling allows for larger, more aggressive adjustments when CPU utilization exceeds thresholds, avoiding the slower, linear response of target tracking. This dual approach ensures the application can handle spikes without over-provisioning or under-provisioning.

Answer

Use predictive scaling based on historical traffic patterns.

Answer

Use manual scaling by increasing the desired capacity before expected spikes.

Answer

Use a target tracking scaling policy based on average CPU utilization.