DOP-C02 Resilient Cloud Solutions Practice Test 9 — 15 Questions

Question 1

A company is deploying a critical web application on AWS and needs to ensure high availability and disaster recovery across multiple AWS Regions. The application uses an Application Load Balancer (ALB) in the primary Region and an Amazon RDS Multi-AZ DB instance. Which TWO actions should the company take to meet these requirements? (Choose two.)

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

Accepted Answer

Use AWS Global Accelerator with endpoint groups in multiple Regions.. AWS Global Accelerator provides static IP addresses and routes traffic to the optimal endpoint across regions, supporting active-passive failover for multi-region disaster recovery. Option E is correct because Amazon Route 53 with a failover routing policy and health checks can monitor the primary ALB's health and automatically route traffic to a secondary ALB in another region if the primary fails. Option A is wrong because RDS Multi-AZ only provides high availability within a single region, not cross-region disaster recovery. Option B is wrong because Amazon CloudFront is a content delivery network, not designed for regional failover routing; it can distribute content but does not provide active-passive failover across regions. Option C is wrong because Auto Scaling groups are for scaling compute capacity within a region, not for cross-region failover.

Answer

Configure an Amazon RDS Multi-AZ deployment in a secondary Region.

Answer

Set up Amazon CloudFront with multiple origins pointing to each Region's ALB.

Answer

Create an Auto Scaling group in the secondary Region that automatically scales up when the primary fails.

Question 2

A company runs a stateful web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application stores session data in local instance memory. To improve resiliency, the company wants to make the application stateless and distribute the load across multiple Availability Zones. Which THREE actions should the company take? (Choose three.)

Accepted Answer

Configure the ALB to distribute traffic across EC2 instances in multiple Availability Zones.. Distributing traffic across EC2 instances in multiple Availability Zones improves availability and fault tolerance, a key aspect of resilient architecture. Option D is correct: implementing an ElastiCache cluster provides a centralized, external session store, making the application stateless. Option E is correct: Amazon DynamoDB is a fully managed, durable, and scalable database service suitable for storing session state externally, further enabling statelessness. Option A is incorrect: enabling sticky sessions (session affinity) would tie a user's session to a specific instance, which works against making the application stateless and reduces resilience. Option B is incorrect: replacing the ALB with an NLB would not help with statelessness; an NLB operates at layer 4 and lacks HTTP-specific features like path-based routing and session management, making it less suitable for web applications.

Answer

Enable sticky sessions (session affinity) on the ALB.

Answer

Replace the ALB with a Network Load Balancer (NLB) to improve performance.

Question 3

A company runs a production application on Amazon ECS with Fargate, fronted by an Application Load Balancer (ALB). The application experiences periodic latency spikes and occasional 502 errors. The ECS service is configured with a desired count of 2 tasks, and the ALB health check is set to /health with a 30-second interval and 2 consecutive failures threshold. The team uses CloudWatch Container Insights and has noticed that CPU and memory utilization of tasks remain below 50%. However, the ALB TargetGroup's HealthyHostCount metric occasionally drops to 0 for a few minutes before recovering. The deployment strategy is rolling update with a minimum healthy percent of 50% and maximum percent of 200%. The team recently updated the task definition to increase memory and CPU, but the issue persists. What is the MOST likely cause of the problem?

Accepted Answer

The ALB health check is too aggressive, causing tasks to be marked unhealthy during brief initialization or deployment.. The health check interval (30 seconds) and failure threshold (2) mean it takes up to 60 seconds to mark a task unhealthy. During deployments, the rolling update may temporarily have only 1 healthy task (minimum 50% of 2 = 1), and if that task becomes unhealthy, HealthyHostCount drops to 0. Option A is wrong because CPU and memory are below 50%, so resource limits are not the issue. Option C is wrong because a target group with 2 tasks and 2 AZs is fine; the problem is not AZ-specific. Option D is wrong because ECS service-linked role does not affect health checks.

Answer

The ECS service role lacks permissions to register targets with the ALB.

Answer

The ALB target group is configured with only one Availability Zone, causing loss of all targets when that AZ fails.

Answer

The task's CPU or memory limits are set too low, causing the container to be throttled.

Question 4

A company runs a critical web application on EC2 instances behind an Application Load Balancer. To improve resilience, they want to automatically replace unhealthy instances. Which AWS feature should they use?

Accepted Answer

Auto Scaling group with ELB health checks. Auto Scaling groups with ELB health checks automatically replace unhealthy instances by terminating and launching new ones. AWS Lambda functions can also be used to check health and launch new instances, providing a custom automation solution. Option A is the native recommended approach, while option C is a valid custom implementation. Option B is wrong because CloudWatch alarms can terminate instances but do not automatically launch replacements; Auto Scaling is needed. Option D is wrong because ELB health checks only mark instances unhealthy; they do not perform any replacement action.

Answer

CloudWatch alarm that terminates the instance

Answer

Elastic Load Balancer health checks

Question 5

A company has a stateless web application on EC2 instances behind an ALB. They want to ensure that if an entire Availability Zone fails, the application remains available with minimal impact. Which architecture best meets this requirement?

Accepted Answer

Deploy the application in two AZs with an Auto Scaling group and an ALB that is enabled for multiple AZs. Deploying EC2 instances in two AZs with an Auto Scaling group and a multi-AZ ALB ensures that if one AZ fails, the ALB can route traffic to healthy instances in the other AZ, providing high availability with minimal impact. Option A is incorrect: a global secondary index in DynamoDB is used to improve query performance, not to provide compute-layer high availability; the application is stateless on EC2, so resilience depends on the compute and load balancer layer. Option B is incorrect: although EC2 instances are in two AZs, a single-AZ ALB is a single point of failure; if that AZ fails, the ALB becomes unavailable. Option D is incorrect: deploying in a single AZ creates a single point of failure; Auto Scaling within that AZ cannot recover from an AZ failure.

Answer

Use a global secondary index in DynamoDB to replicate data across regions

Answer

Deploy EC2 instances in two AZs but use a single-AZ ALB

Answer

Deploy the application in a single AZ with an Auto Scaling group that launches instances in the same AZ

Question 6

A company runs a stateful application on EC2 instances. They want to distribute traffic evenly and maintain session stickiness. Which AWS service should they use?

Accepted Answer

Application Load Balancer with sticky sessions. An Application Load Balancer with sticky sessions (session affinity) ensures that a client's requests are sent to the same target. Option A is wrong because Network Load Balancer does not natively support sticky sessions based on application cookies. Option C is wrong because Route53 weighted routing does not handle session stickiness. Option D is wrong because CloudFront can forward cookies but is not primarily for load balancing.

Answer

Network Load Balancer

Answer

Amazon Route 53 weighted routing policy

Answer

Amazon CloudFront with origin failover

Question 7

A company uses AWS CodeDeploy to deploy a new version of an application to EC2 instances. They want to minimize downtime and roll back quickly if the deployment fails. Which deployment type should they use?

Accepted Answer

Blue/green deployment. Blue/green deployment creates two separate environments (blue and green) and shifts traffic from the old to the new after testing. This minimizes downtime because traffic is switched instantly, and rollback is achieved by reverting traffic to the original environment. Option A (Canary) is a traffic shifting pattern used within blue/green deployments, not a standalone deployment type that offers immediate rollback. Option B (Linear) is also a traffic shifting pattern for blue/green. Option D (In-place) updates existing instances, causing downtime during deployment and requiring a manual rollback process.

Answer

Canary deployment

Answer

Linear deployment

Answer

In-place deployment

Question 8

A company runs a critical microservices architecture on Amazon ECS with Fargate. They want to ensure that if a task fails, it is automatically restarted, and the service remains available across multiple Availability Zones. How should they configure the ECS service?

Accepted Answer

Define an ECS service with a task definition, set desired count across multiple Availability Zones, and use Service Auto Scaling. An ECS service configured with a task definition, desired count across multiple Availability Zones, and Service Auto Scaling ensures resilience. The ECS service scheduler automatically restarts failed tasks, and distributing tasks across AZs provides high availability. Option A is wrong because placing all tasks in a single AZ creates a single point of failure. Option B is wrong because a standalone Fargate task does not have automatic restart; a CloudWatch alarm can restart it but lacks the built-in resilience of an ECS service. Option C is wrong because using a single EC2 instance is a single point of failure and does not provide multi-AZ resilience.

Answer

Place all tasks in the same Availability Zone to reduce latency

Answer

Run a standalone Fargate task and use a CloudWatch alarm to restart it

Answer

Use an EC2 launch type with a single instance to reduce complexity

Question 9

A company runs a global web application on EC2 instances behind an ALB in us-east-1. They want to improve resilience by routing users to the nearest healthy region. Which service should they use?

Accepted Answer

Amazon Route 53 latency-based routing with health checks. Amazon Route 53 latency-based routing with health checks routes users to the region with the lowest latency and only to healthy endpoints. Option A is wrong because AWS Global Accelerator uses anycast IP to route to the nearest edge location and can distribute traffic across regions, but it does not provide direct latency-based routing to the nearest healthy region; Route 53 is more straightforward for this use case. Option B is wrong because Application Load Balancer cross-zone load balancing only distributes traffic across availability zones within a single region, not across regions. Option D is wrong because Amazon CloudFront with multiple origins is a content delivery network that caches content at edge locations; it can route to multiple origins, but it is not primarily designed for routing users to the nearest healthy region based on latency—Route 53 provides more precise latency-based routing.

Answer

AWS Global Accelerator

Answer

Application Load Balancer cross-zone load balancing

Answer

Amazon CloudFront with multiple origins

Question 10

A company uses Amazon DynamoDB with global tables for a multi-region active-active application. They notice that occasionally, concurrent updates to the same item in different regions cause data inconsistency. How can they resolve this?

Accepted Answer

Use conditional writes and design the application to handle conflicts. DynamoDB global tables use an eventually consistent model for multi-region replication, meaning concurrent updates to the same item in different regions can lead to conflicts. Conditional writes allow the application to enforce a last-writer-wins (LWW) strategy or custom conflict resolution logic, ensuring data consistency by only applying updates that meet specified conditions (e.g., a version number or timestamp check). This approach aligns with the recommended practice for handling concurrent writes in an active-active global table setup.

Answer

Disable global tables and use a single region

Answer

Use DynamoDB read replicas instead of global tables

Answer

Use DynamoDB Accelerator (DAX) to cache writes

Question 11

A company experiences intermittent high latency for a web application running on EC2 behind an ALB. They want to monitor and automatically replace instances that have high CPU. Which solution meets this requirement?

Accepted Answer

Create a CloudWatch alarm on CPU utilization that triggers an Auto Scaling policy to replace the instance. You can configure a CloudWatch alarm on the EC2 instance's CPU utilization metric, and then use that alarm to trigger an Auto Scaling lifecycle hook or a scaling policy that terminates the unhealthy instance and launches a replacement. This directly ties performance monitoring to automated instance replacement, meeting the requirement to replace instances with high CPU.

Answer

Use Auto Scaling scheduled scaling actions to replace instances at peak times

Answer

Use AWS Lambda to periodically check CPU and terminate high-CPU instances

Answer

Configure the ALB health check to mark instances unhealthy when CPU is high

Question 12

Which TWO AWS services can be used to distribute incoming traffic across multiple AWS resources in different Availability Zones within a single region?

Accepted Answer

AWS Global Accelerator. AWS Global Accelerator uses the AWS global network and Anycast static IP addresses to route incoming traffic to the optimal endpoint, such as an Application Load Balancer or EC2 instance, across multiple Availability Zones within a single region. It improves performance and reliability by directing traffic to the healthiest endpoint and automatically rerouting in case of failure, making it a valid service for distributing traffic across AZs.

Answer

Amazon Route 53

Answer

Amazon CloudFront

Answer

AWS Direct Connect

Question 13

Which THREE strategies can improve the resilience of an Amazon RDS for PostgreSQL database?

Accepted Answer

Enable automated backups with a retention period. Multi-AZ deployment (E) provides automatic failover to a standby instance in a different Availability Zone, enhancing availability. Automated backups with a retention period (B) enable point-in-time recovery, reducing data loss. Read replicas in another Availability Zone (C) offload read traffic and can be promoted to a standalone instance during a disaster. Option A is wrong because disabling backups removes recovery capability, sacrificing resilience. Option D is wrong because a single-AZ instance has no failover and is less resilient.

Answer

Disable automated backups to save costs

Answer

Use a single-AZ instance to reduce complexity

Question 14

Which TWO actions can help ensure that an application running on EC2 instances can survive the loss of an entire Availability Zone?

Accepted Answer

Use an Auto Scaling group with multiple Availability Zones. Deploying instances in multiple Availability Zones (AZs) ensures that if one AZ fails, instances in other AZs continue to run. Using an Auto Scaling group with multiple AZs automatically distributes instances across AZs and replaces failed instances, further enhancing resilience. Options B and C are both correct because they achieve multi-AZ deployment. Option A is incorrect because a single AZ is a single point of failure. Option D is incorrect because instance type does not provide AZ resilience. Option E is incorrect because CloudWatch alarms can detect issues but do not distribute instances across AZs.

Answer

Deploy all instances in a single Availability Zone for consistency

Answer

Use a larger instance type to handle more load

Answer

Use CloudWatch alarms to monitor instance health

Question 15

A company runs a microservices architecture on Amazon ECS with Fargate. Services communicate via an internal Application Load Balancer. Recently, one service became unavailable due to a memory leak, causing cascading failures in downstream services. What design change would MOST effectively improve resilience and limit the blast radius?

Accepted Answer

Implement circuit breaker patterns in the service discovery and client libraries to stop calling unhealthy services.. Implementing a circuit breaker pattern in service discovery and client libraries stops requests to unhealthy services, preventing cascading failures and limiting blast radius. Option A is wrong because increasing memory limits only delays the inevitable failure and does not prevent downstream services from being affected. Option C (connection draining) only affects in-flight requests during deregistration, not active health issues. Option D (auto scaling) helps but does not stop requests from being sent to a failing service; scaling cannot fix a memory leak.

Answer

Increase the memory limit for each ECS task to accommodate memory leaks.

Answer

Enable connection draining on the ALB to allow in-flight requests to complete.

Answer

Implement automatic scaling policies for ECS services based on memory utilization.