DOP-C02 · domain
Resilient Cloud Solutions
This domain covers designing and operating systems that stay available and recover from failure on AWS. Questions present scenarios about Multi-AZ and multi-Region architectures, Auto Scaling, SQS decoupling, DynamoDB global tables, EMR fault tolerance, and disaster recovery strategies, asking you to pick the configuration that meets resilience goals without overspending or over-engineering.
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What to know about Resilient Cloud Solutions
You must be able to select the right resilience mechanism per scenario: Multi-AZ for high availability, multi-Region for disaster recovery, Auto Scaling for elasticity, and managed replication for data stores. The single most important thing is matching the failure scope (AZ vs Region vs instance) to the correct AWS feature.
Designing Multi-AZ Auto Scaling groups with ELB health checks and cross-zone load balancing
Choosing DynamoDB global tables for multi-Region active-active writes and low latency
Configuring SQS visibility timeout, dead-letter queues, and scaling consumers to drain backlogs
Selecting EMR instance fleets and Spot with fallback for fault-tolerant batch jobs
Watch out for
Common Resilient Cloud Solutions exam traps
- ▸Assuming a single-AZ RDS deployment survives an AZ failure; Multi-AZ standby is required for automatic failover
- ▸Setting SQS visibility timeout shorter than consumer processing time, causing duplicate deliveries and growing backlog
- ▸Treating DynamoDB global tables as strongly consistent across Regions; they use last-writer-wins conflict resolution
Question index
All Resilient Cloud Solutions questions (184)
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A company runs a critical application on AWS Lambda that processes messages from an Amazon SQS queue. The application must be resilient to downstream service failures. The team notices that when the downstream service is unhealthy, messages are repeatedly retried and eventually sent to the dead-letter queue (DLQ) before the service recovers. What design change would improve resilience by allowing automatic retries after the downstream service recovers?
Hard2A company is deploying a critical microservice on Amazon ECS with Fargate. They need to ensure that the service can tolerate an Availability Zone failure. What is the BEST approach?
Medium3A company wants to ensure that its Amazon S3 bucket is resilient to accidental deletion of objects. Which TWO actions should be taken?
Easy4A DevOps engineer is responsible for a critical application that uses an Amazon Aurora MySQL cluster. The application experiences sudden spikes in read traffic. The engineer needs to ensure that read replicas automatically scale to handle the load and that the application can tolerate the failure of an Availability Zone without manual intervention. Which solution should the engineer implement?
Hard5A 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?
Medium6A DevOps team is designing a disaster recovery solution for an Amazon RDS for MySQL database. The primary database is in us-east-1, and the recovery point objective (RPO) is 5 minutes, recovery time objective (RTO) is 1 hour. Which solution meets these requirements?
Medium7A company runs a stateless web application on Amazon ECS with Fargate. The application must be highly available across multiple Availability Zones. What is the BEST way to achieve this?
Medium8A company runs a stateless web application on EC2 instances in an Auto Scaling group across three Availability Zones. The application uses an Application Load Balancer. The operations team needs to ensure that the application remains available if one AZ fails. Which solution is MOST resilient?
Easy9A company is deploying a serverless application using AWS Lambda, Amazon API Gateway, and Amazon DynamoDB. The application must be resilient to regional outages. Which THREE steps should the company take to achieve multi-Region resilience? (Choose THREE.)
Medium10A company runs a stateless web application on AWS Lambda behind an Application Load Balancer (ALB). During a deployment, the team updates the Lambda function to a new version. Some users report seeing the old version of the application for several minutes after the deployment. What is the MOST likely cause?
Hard11A 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?
Medium12A 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?
Hard13A company runs a critical application on AWS that uses an Auto Scaling group of EC2 instances. The application must remain available even if an entire Availability Zone fails. Which THREE actions should the company take?
Hard14A startup runs a stateless web application on AWS Elastic Beanstalk with a single environment. The application uses an Amazon RDS for MySQL database instance. The startup is preparing for a marketing campaign that is expected to increase traffic by 10x. The CTO is concerned about the application's ability to handle the load and wants to ensure high availability and resilience. The current architecture has a single RDS instance (db.t3.medium) and a single Elastic Beanstalk environment with one EC2 instance (t3.medium). The startup has a limited budget but wants to improve resilience without over-provisioning. Which combination of actions should the DevOps engineer recommend? (Choose THREE.)
Easy15A company is building a serverless application using AWS Lambda, Amazon API Gateway, and Amazon DynamoDB. The application must be resilient to sudden spikes in traffic without manual intervention. Which combination of services should be used?
Medium16A 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?
Medium17A company is building a global application that requires low-latency access to static content across multiple AWS Regions. The content changes infrequently. Which solution is MOST resilient and cost-effective?
Hard18Refer to the exhibit. An IAM policy is attached to a user. A developer tries to upload an object to s3://my-bucket/confidential/report.pdf without specifying server-side encryption. What will happen?
Hard19An AWS account owner (Account A) owns an S3 bucket named my-bucket. The bucket policy shown in the exhibit is attached to the bucket. A user from Account B attempts to upload an object to the bucket without specifying the x-amz-acl header. What will happen?
Hard20A 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?
Hard21A 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?
Easy22A company uses Amazon RDS Multi-AZ for disaster recovery. The primary DB instance in us-east-1a fails. What happens next?
Medium23A company runs a stateless web application on EC2 instances behind an Application Load Balancer. To improve resilience, which configuration should be used for the EC2 instances?
Easy24A company wants to ensure that its Amazon S3 bucket can withstand the loss of an entire AWS Availability Zone. Which configuration meets this requirement?
Easy25A company runs a critical application on AWS using Amazon EC2 instances in an Auto Scaling group, an Application Load Balancer (ALB), and an Amazon RDS for PostgreSQL Multi-AZ DB cluster. The application must maintain an RTO of 5 minutes and an RPO of 1 second for database transactions. The current setup meets these requirements, but the DevOps team wants to improve the resilience of the application tier to withstand a regional failure. Which THREE actions should be taken? (Choose three.)
Hard26A 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.)
Medium27A company is designing a disaster recovery strategy for its application. The application runs on EC2 instances and uses an RDS MySQL database. The RTO is 1 hour, and the RPO is 15 minutes. Which TWO approaches meet these requirements?
Easy28A company runs a microservices architecture on Amazon ECS with Fargate. Each service is deployed in its own ECS service. The company wants to ensure that if one Availability Zone (AZ) fails, the services can continue to operate with minimal impact. What is the MOST resilient task placement strategy?
Hard29A company runs a critical application on Amazon EC2 instances in an Auto Scaling group. To ensure high availability, the instances are deployed across three Availability Zones. Which additional step should the company take to protect against a regional failure?
Easy30A company is designing a highly available architecture for a web application using AWS services. The application must be resilient to the failure of an entire AWS Region. Which TWO strategies should the company implement? (Choose TWO.)
Medium31A company is deploying a web application on Amazon ECS with Fargate. The application consists of a frontend service and a backend service. The DevOps team needs to ensure that the frontend service can communicate with the backend service securely without exposing the backend to the internet. Which THREE steps should the team take? (Choose THREE.)
Easy32A company runs a critical application on EC2 instances in an Auto Scaling group behind an ALB. They want to ensure that if an instance fails, the application remains available with minimal disruption. Which combination of services provides the best resilience?
Hard33A DevOps engineer runs the above command and sees that instance i-0abcd1234efgh5678 is unhealthy with reason 'Target.Timeout'. The instance is running and the application on port 80 responds to curl from the instance itself. What is the MOST likely cause?
Medium34An IAM policy is attached to an S3 bucket to allow access from a specific VPC CIDR range. However, users from the VPC are receiving 'Access Denied' errors when trying to access objects in the bucket. What is the MOST likely reason?
Medium35A company is designing a disaster recovery (DR) strategy for a stateless web application deployed on Amazon ECS with Fargate. The application is fronted by an Application Load Balancer (ALB) and uses Amazon ElastiCache for Redis for session state. The primary region is us-east-1. The DR plan requires a Recovery Point Objective (RPO) of 15 minutes and a Recovery Time Objective (RTO) of 30 minutes. Which solution meets these requirements with the LEAST operational overhead?
Hard36A 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?
Easy37A company's application runs on Amazon EC2 instances in an Auto Scaling group. The application writes logs to local instance storage. The operations team needs to ensure logs are not lost during instance termination or scaling events. What should be done?
Hard38A company runs a stateless web application on a fleet of EC2 instances in an Auto Scaling group. The application stores session state in a shared ElastiCache Redis cluster. During traffic spikes, the application becomes slow. Monitoring shows that the Redis cluster has high CPU utilization. Which solution is MOST cost-effective and scalable?
Medium39A company hosts a static website on Amazon S3 with a CloudFront distribution. The website is critical for business operations and must be available even if the primary AWS Region fails. Currently, the S3 bucket is in us-east-1, and CloudFront uses that bucket as the origin. The company has a secondary bucket in us-west-2 with a replica of the data. The company wants to use CloudFront to automatically fail over to the secondary bucket if the primary becomes unavailable. The DevOps engineer needs to implement a solution that requires minimal operational overhead. What should the engineer do?
Medium40A company runs a critical web application on EC2 instances behind an Application Load Balancer. The application stores session state in an in-memory cache on each instance. During deployment of a new version, users experience session timeouts and errors. Which design change will MOST effectively improve resilience and avoid session loss during deployments?
Medium41A company is designing a serverless application using AWS Lambda, Amazon API Gateway, and Amazon DynamoDB. The application must tolerate a Regional failure. Which design provides the most resilience?
Medium42A company uses AWS Lambda functions to process events from Amazon SQS. The Lambda function sometimes fails due to timeouts. The team wants to preserve the event for reprocessing. How should they configure the integration?
Hard43A company runs a stateful web application on EC2 instances in an Auto Scaling group. The application uses an Application Load Balancer (ALB) and an Amazon ElastiCache Redis cluster. Users report that after a scaling event, they are logged out and lose session data. What is the most likely cause?
Hard44A company runs a stateless web application on Amazon ECS with Fargate launch type. The application experiences intermittent traffic spikes. The company wants to ensure that the application can scale automatically and remain resilient to underlying infrastructure failures. Which combination of actions should the DevOps engineer take?
Hard45A company runs a containerized application on Amazon ECS with Fargate. The application needs to be resilient to Availability Zone failures. Which THREE actions should the company take? (Choose THREE.)
Hard46A company is designing a multi-Region disaster recovery strategy for a stateless web application. The application runs on EC2 instances in an Auto Scaling group behind an ALB in us-east-1. The recovery point objective (RPO) is 15 minutes and recovery time objective (RTO) is 30 minutes. The application data is stored in Amazon RDS for PostgreSQL. Which combination of actions should the company take to meet the RPO and RTO?
Hard47A company uses Amazon ECS with Fargate for containerized applications. They need to ensure that if a task fails, it is automatically restarted and the application remains available. Which THREE actions should they take? (Choose THREE.)
Hard48A 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.)
Medium49A 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?
Hard50A company is designing a multi-region disaster recovery strategy for a stateless web application. They want to minimize RTO and RPO. Which TWO of the following should they implement? (Choose TWO.)
Medium51A company wants to design a resilient architecture for a web application using AWS services. Which of the following is a best practice for improving resilience?
Easy52A company runs a microservices application on Amazon ECS with Fargate launch type. The application experiences intermittent failures when calling an external API. The errors are transient and usually resolve within a few seconds. How should the company improve resilience?
Medium53A 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?
Medium54A company runs a critical batch processing workload on Amazon EMR that must complete within a 2-hour window each night. The workload is fault-tolerant but must be resilient to instance failures. Currently, the EMR cluster uses instance fleets with Spot Instances. Recently, Spot Instance interruptions caused the cluster to take over 3 hours to complete. Which change will MOST effectively ensure the workload completes within the 2-hour window despite Spot interruptions?
Hard55A 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?
Medium56Drag and drop the steps to troubleshoot a failed deployment in AWS CodeDeploy into the correct order.
Medium57A company's application runs on EC2 instances in a single Availability Zone. The operations team wants to improve resilience without redesigning the application. Which action is the MOST effective?
Easy58A 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?
Easy59A company runs a critical e-commerce platform on AWS. The architecture includes an Application Load Balancer (ALB) that distributes traffic to a fleet of EC2 instances in an Auto Scaling group across three Availability Zones. The instances run a Java application that connects to an Amazon RDS Multi-AZ MySQL database. The application also uses Amazon ElastiCache for Redis for session caching. The company recently experienced a severe outage where the ALB's 5xx error rate spiked to 100% for 45 minutes. The root cause was a combination of a slow-running query on the RDS primary instance and a subsequent failover that caused the application to lose connections to the database. The failover happened because the slow query caused the primary to become unresponsive, triggering a Multi-AZ failover. During the failover, the application's connection pool exhausted, and new connections failed. The application logs show a high rate of 'java.sql.SQLTimeoutException' and 'com.mysql.cj.exceptions.CJCommunicationsException'. The DevOps team needs to implement a long-term solution that minimizes the impact of similar incidents. The solution must be cost-effective and require minimal application changes. Which combination of actions should the DevOps team take?
Hard60A company runs a critical microservice on Amazon ECS with AWS Fargate. The service must be highly available across multiple Availability Zones. The DevOps engineer configured the service with a desired count of 4 tasks spread across 2 Availability Zones. During a deployment, a new task fails to start due to a missing environment variable. The deployment fails, but the old tasks continue to run. What is the most likely cause of the deployment failure and how can the engineer ensure future deployments are resilient?
Hard61A company runs a Stateful application on EC2 that requires sticky sessions. They use an ALB with duration-based stickiness. During a deployment, they want to drain existing connections gracefully before terminating instances. Which step is necessary?
Hard62Refer to the exhibit. A Lambda function uses the IAM role with the above policy. The function is configured to access a DynamoDB table MyTable and an RDS instance in a VPC. When invoked, the function fails with an error indicating it cannot describe VPC subnets. What is the MOST likely cause?
Hard63A company runs a static website on Amazon S3 with public read access. The website content is stored in an S3 bucket and served through an Amazon CloudFront distribution for better performance and security. Recently, the company noticed that some users are accessing the S3 bucket directly via the S3 endpoint, bypassing CloudFront. This increases costs and exposes the bucket to potential attacks. The company wants to ensure that all access to the website goes through CloudFront only. Which solution should the company implement?
Easy64A company runs a containerized application on Amazon EKS. They want to ensure that if a node fails, the pods are rescheduled on healthy nodes. Which configuration is necessary?
Medium65A company runs a production e-commerce platform on AWS. The architecture includes an Application Load Balancer (ALB) that distributes traffic to a fleet of Amazon EC2 instances running in an Auto Scaling group across three Availability Zones (AZs). The application stores session state in Amazon ElastiCache for Redis (cluster mode disabled) with a single node. The database is an Amazon Aurora MySQL DB cluster with one writer and two reader instances in different AZs. The platform experiences intermittent slowdowns and occasional timeouts during peak traffic hours. The CloudWatch metrics show that the ALB's TargetResponseTime is elevated, and the Redis CPU utilization is consistently above 80% during these periods. The Auto Scaling group is scaling out, but new instances take several minutes to become healthy. The DevOps team has been asked to improve the resilience and performance of the application with minimal changes to the application code. Which solution should the team implement?
Hard66A company runs a high-traffic web application on a fleet of EC2 instances behind an Application Load Balancer (ALB) with Auto Scaling. The application uses an Amazon RDS for PostgreSQL database. Recently, during a traffic spike, the application became unresponsive. Investigation revealed that the database CPU utilization reached 100%, causing queries to timeout. The Auto Scaling group added more EC2 instances, which only increased the load on the database. The DevOps team needs to implement a solution that prevents the database from being overwhelmed during traffic spikes while maintaining application availability. The solution must be cost-effective and require minimal changes to the application code. Which solution should the DevOps team implement?
Hard67A company runs a stateful web application on EC2 instances behind a Network Load Balancer (NLB) in a single Availability Zone. The application stores session state locally on the instance. The company wants to achieve high availability across multiple AZs with minimal application changes. What should the DevOps engineer do?
Hard68A company's application uses Amazon DynamoDB as its primary data store. The application experiences occasional throttling errors during traffic spikes. The DevOps team needs to implement a solution that ensures consistent performance without manual intervention. Which TWO actions should the team take? (Choose TWO.)
Hard69A company is implementing a disaster recovery strategy for its Amazon Aurora MySQL database. The primary database is in us-west-2. The company requires an RPO of less than 1 minute and an RTO of less than 5 minutes. Which solution meets these requirements?
Hard70A company runs a stateful web application on EC2 instances that store session data locally. They want to migrate to a stateless architecture for better resilience. Which TWO actions should they take?
Medium71A company runs a serverless application using AWS Lambda functions behind an Amazon API Gateway. The application processes user uploads stored in an S3 bucket. The Lambda function writes results to a DynamoDB table. Recently, the function started timing out when processing large files. What should the DevOps engineer do to improve resilience for large file processing?
Easy72A 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?
Easy73A company has a microservices architecture running on Amazon ECS with Fargate launch type. Each service is deployed in multiple Availability Zones. The services communicate via REST APIs. Recently, a downstream service experienced a partial outage, causing upstream services to time out and leading to cascading failures. The team wants to improve resilience against such failures. Which combination of actions should the DevOps engineer take? (Choose TWO.)
Hard74A company runs a microservices application on Amazon ECS with Fargate. The application includes a service that processes orders and stores them in an RDS PostgreSQL database. The company wants to ensure that the order service is resilient to AZ failures and can handle a sudden increase in order volume. Which TWO actions should the DevOps engineer take? (Choose TWO.)
Medium75A 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?
Medium76An e-commerce platform uses Amazon DynamoDB as its primary database. The platform experiences occasional read throttling during flash sales. The operations team needs to ensure that read traffic is handled without errors, while keeping costs low. What should a DevOps engineer recommend?
Medium77A company is deploying a critical application on Amazon EC2 instances behind an Application Load Balancer (ALB) across multiple Availability Zones. The application must be resilient to the failure of an entire Availability Zone. Which design should the company implement?
Easy78A 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?
Medium79An organization runs a critical application on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. The application requires that all traffic be encrypted in transit. The security team mandates the use of TLS 1.2 or higher and specific ciphers. What is the MOST efficient way to enforce this requirement?
Hard80A company wants to design a highly available and fault-tolerant architecture for a stateless web application on AWS. Which TWO actions should they take? (Choose two.)
Easy81A company runs a stateful application on EC2 instances. They want to distribute traffic evenly and maintain session stickiness. Which AWS service should they use?
Medium82A company runs a critical web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application frequently experiences high latency during peak hours. The DevOps team needs to implement a solution that automatically adds capacity based on demand and reduces cost during off-peak hours. Which combination of AWS services should the team use?
Hard83A development team wants to ensure that their application can continue serving traffic even if an entire AWS Availability Zone (AZ) becomes unavailable. The application runs on Amazon EC2 instances in an Auto Scaling group and uses an Application Load Balancer (ALB). Which configuration should the team implement to meet this requirement?
Easy84A DevOps engineer is designing a resilient architecture for a serverless application using AWS Lambda, Amazon API Gateway, and Amazon DynamoDB. The application experiences occasional spikes in traffic that cause Lambda function throttling and increased error rates. What is the MOST effective way to improve resilience and reduce throttling?
Easy85A DevOps team is designing a disaster recovery plan for an RDS MySQL database. The database must be recoverable with minimal data loss in case of a regional failure. Which solution provides the LOWEST Recovery Point Objective (RPO)?
Easy86A company runs a high-traffic e-commerce application on EC2 instances in an Auto Scaling group behind an ALB. The application uses an in-memory cache on the EC2 instances. During a recent deployment, the Auto Scaling group terminated an instance that had active user sessions, causing users to lose their cart data and leading to a poor customer experience. The company wants to prevent this in future deployments. They need a solution that allows existing sessions to complete before instance termination, without manual intervention. Which solution should they use?
Medium87A company wants to protect its application from DDoS attacks. Which THREE AWS services should they use?
Easy88A 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?
Hard89A company uses AWS CloudFormation to deploy a multi-tier application. During an update, the stack fails and rolls back. The rollback also fails, leaving the stack in UPDATE_ROLLBACK_FAILED state. The operations team needs to resolve this with minimal disruption. What is the MOST efficient approach?
Hard90A company deploys the above CloudFormation stack. They want to enforce HTTPS for all requests to the S3 bucket. After deployment, users are still able to make HTTP requests. What is the problem?
Hard91A 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?
Medium92A company has a serverless application using AWS Lambda functions that process messages from an Amazon SQS queue. The Lambda function sometimes fails due to transient errors. The company wants to ensure that failed messages are retried and eventually processed or sent to a dead-letter queue after 3 retries. What is the correct configuration?
Hard93A company uses AWS CloudFormation to deploy infrastructure. The stack creation fails with the error: 'Resource handler returned message: 'The security group does not exist in VPC'.' The template references a security group by name. What is the MOST likely cause?
Hard94A company is designing a disaster recovery strategy for a critical application that requires a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 1 hour. The application runs on EC2 with data stored in Amazon RDS Multi-AZ. Which approach meets these requirements?
Medium95A DevOps engineer ran the above command and saw this output. What is the MOST likely cause of the stack creation failure?
Medium96A company is building a multi-tier web application on AWS. The web tier runs on EC2 instances behind an ALB. The application tier runs on EC2 instances that are not publicly accessible. The database tier runs on RDS MySQL. Which design provides the HIGHEST level of resilience for the database tier?
Easy97A company runs a containerized application on Amazon EKS. The application must be highly available across multiple Availability Zones and must automatically recover from node failures. Which THREE steps should be taken?
Hard98A company runs a critical application on Amazon ECS with the Fargate launch type. The application is deployed across three Availability Zones. Each service has its own Application Load Balancer. The company wants to implement a blue/green deployment strategy to reduce risk. They currently use AWS CodeDeploy for ECS deployments. During a recent deployment, the company noticed that the new version (green) was not receiving any traffic even after passing all health checks. The CodeDeploy configuration uses a 'Linear10PercentEvery3Minutes' traffic shifting configuration. What is the most likely reason that the green tasks are not receiving traffic?
Hard99A company is designing a highly available architecture for a web application using AWS. Which TWO of the following design principles should be applied? (Select TWO.)
Easy100A company is designing a resilient architecture for a critical application. Which TWO strategies improve resilience?
Medium101A DevOps engineer runs the above command and sees that one target is unhealthy with a 503 error. The application is a web server running on port 80. The health check is configured to hit the root path '/'. Which action should the engineer take to resolve the issue?
Hard102A 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.)
Hard103An 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?
Hard104A company's application uses Amazon SQS to decouple microservices. During peak hours, the SQS queue backlog grows significantly, causing processing delays. The DevOps team wants to reduce latency without increasing costs unnecessarily. What should the team do?
Medium105An application on EC2 instances in an Auto Scaling group uses an ALB. The ALB health checks are failing for some instances, but the instances are healthy from the OS perspective. What is the most likely cause?
Medium106A media company runs a video processing pipeline on AWS. Raw videos are uploaded to an S3 bucket, which triggers a Lambda function to start an AWS Batch job for transcoding. The Batch job reads the source video from S3, processes it, and writes the output to another S3 bucket. Recently, the company has seen an increase in processing failures. Investigation shows that the Batch jobs are being terminated with a 'TIMEOUT' status after running for exactly 30 minutes. The video files are large, and some jobs legitimately take up to 45 minutes. The Batch job definition has a 'timeout' setting configured. Which action should be taken to resolve this issue?
Medium107A company runs a critical web application on EC2 instances in an Auto Scaling group. The application uses an Application Load Balancer (ALB) with health checks pointing to /health. Recently, the application experienced intermittent failures where the ALB would mark instances as unhealthy and route traffic away, causing a reduction in capacity. The development team noticed that the /health endpoint occasionally returns HTTP 503 when the application is under heavy load, but the application can recover quickly. The team wants to avoid unnecessary instance replacements while ensuring availability. Which solution should the DevOps engineer implement?
Hard108A company runs a microservices application on Amazon EKS. The application's frontend service needs to communicate with the backend service. The DevOps team wants to implement service-to-service authentication using AWS IAM. Which method should the team use?
Hard109Which THREE components are required to implement a global application that can withstand the failure of an entire AWS Region? (Select THREE.)
Hard110Which TWO actions can help ensure that an application running on EC2 instances can survive the loss of an entire Availability Zone?
Easy111A company runs a stateful application on EC2 instances in an Auto Scaling group. The application stores state on local instance storage. During a scaling event, users lose session data. How can the company make the application resilient without modifying the application code?
Medium112A DevOps team uses the above CloudFormation template to create an S3 bucket. What does the bucket policy accomplish?
Easy113A company wants to automate the recovery of an Amazon RDS DB instance in a different region if the primary region becomes unavailable. Which service should they use?
Easy114A 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?
Hard115A company is designing a disaster recovery strategy for its primary RDS for PostgreSQL database in us-east-1. The RTO is 15 minutes and RPO is 1 minute. Which solution meets these requirements?
Easy116A 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?
Easy117A company wants to automatically recover an Amazon RDS DB instance if the underlying hardware fails. Which feature should the DevOps engineer enable?
Easy118A DevOps engineer is designing a highly available web application using Amazon Route 53. The application is deployed in two AWS Regions. The engineer wants to route traffic to the nearest healthy endpoint. Which routing policy should be used?
Easy119A DevOps engineer applies this S3 bucket policy to an S3 bucket. What is the effect of this policy?
Hard120A company has deployed a multi-tier application on AWS. The web tier uses an Auto Scaling group of EC2 instances behind an Application Load Balancer. The application tier uses another Auto Scaling group of EC2 instances that process messages from an Amazon SQS queue. The database tier uses Amazon RDS Multi-AZ. Recently, the application experienced a complete outage when the SQS queue became overwhelmed with messages due to a sudden spike in traffic. The application tier could not process messages fast enough, causing the queue to grow indefinitely and eventually exceed the visibility timeout, leading to message loss and degraded performance. The DevOps engineer needs to improve the resilience of the architecture to handle traffic spikes without losing messages. Which solution should be implemented?
Medium121A 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?
Hard122A company is designing a disaster recovery strategy for its on-premises database to AWS using AWS Elastic Disaster Recovery (AWS DRS). The recovery time objective (RTO) is 15 minutes, and the recovery point objective (RPO) is 1 minute. Which configuration should they use?
Easy123A company is designing a disaster recovery plan for an Amazon S3 data lake. The data lake stores sensitive data that must be replicated to a secondary Region with an RPO of 15 minutes. Which THREE actions should the company take? (Choose THREE.)
Hard124A company runs a critical application on EC2 instances behind an Application Load Balancer. The application uses an Amazon RDS for PostgreSQL Multi-AZ DB instance. During a recent failover test, the application experienced a 5-minute downtime. The RDS failover completed within 30 seconds. What is the most likely cause of the prolonged downtime?
Hard125A company uses DynamoDB global tables with two regions. They notice that writes in one region are not replicating to the other region after a brief network partition. Which configuration will ensure replication resumes automatically?
Hard126A company is running a production database on Amazon RDS for PostgreSQL with Multi-AZ deployment. The database experiences a failover due to an AZ outage. What happens to the existing database connections during the failover?
Easy127A company runs a critical REST API on Amazon ECS Fargate behind an Application Load Balancer. The operations team wants the service to automatically recover from a failed task without manual intervention. They have configured a target group health check, but the ECS service still does not replace unhealthy tasks. What should the DevOps engineer do to ensure automatic task replacement?
Medium128Your company runs a multi-tier web application on AWS. The web tier consists of EC2 instances behind an Application Load Balancer (ALB) in an Auto Scaling group across three Availability Zones. The application tier runs on a separate Auto Scaling group of EC2 instances that process requests from the web tier. The database tier uses an Amazon RDS for PostgreSQL Multi-AZ deployment. All application servers write logs to Amazon CloudWatch Logs. Recently, the operations team reported that during peak hours, the web tier experiences intermittent 503 errors. The ALB access logs show that the errors occur when the target group's healthy host count drops to zero momentarily. The Auto Scaling group's minimum and desired capacity is 6, with a maximum of 12. The scaling policy is based on average CPU utilization, with a target of 60%. The health check grace period is 300 seconds. The application health check endpoint returns a 200 status when healthy. The DevOps engineer suspects that the scaling policy is too slow to react to traffic spikes. The engineer wants to implement a more proactive scaling approach. Which solution should the engineer implement?
Medium129A company is building a serverless application using AWS Lambda, Amazon API Gateway, and Amazon DynamoDB. The application is expected to have unpredictable traffic patterns. The DevOps team needs to ensure that the application can handle sudden spikes in traffic without throttling. Which TWO actions should the team take? (Choose TWO.)
Medium130A company runs a web application on AWS that uses Amazon SQS to decouple the frontend from the backend processing. The application experiences sudden spikes in traffic, causing the SQS queue to accumulate a large number of messages. The backend workers are unable to process messages fast enough, leading to increased latency. What solution can the company implement to improve the resilience and scalability of the backend?
Medium131Which TWO AWS services can be used to distribute incoming traffic across multiple AWS resources in different Availability Zones within a single region?
Medium132A company uses AWS Lambda functions to process events from an Amazon SQS queue. The Lambda function occasionally fails due to a transient downstream service error. The DevOps team wants to ensure that failed messages are not lost and can be retried later. The team also wants to reduce the number of invocations on the downstream service. Which configuration should the team use?
Hard133A 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?
Hard134A company wants to ensure its RDS Multi-AZ deployment automatically fails over to a standby instance in a different Availability Zone. Which additional step is required?
Easy135A company is deploying a stateful application on Amazon EKS. The application requires persistent storage that can be reattached to a new pod if the original pod fails. The cluster spans multiple Availability Zones. Which storage solution provides the BEST resilience and meets these requirements?
Medium136A 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?
Medium137A company is designing a highly available architecture for a web application. The application runs on Amazon EC2 instances in an Auto Scaling group across three Availability Zones. The instances are behind an Application Load Balancer (ALB). Which additional step should the team take to ensure that traffic is evenly distributed across all healthy instances in all Availability Zones?
Easy138Which TWO strategies can be used to improve the resilience of an application running on Amazon ECS with Fargate? (Select TWO.)
Medium139A company runs a web application on EC2 instances behind an ALB. To improve resilience, they want to automatically replace failed instances and maintain a minimum number of instances. Which AWS service should be used?
Easy140A 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?
Medium141A company wants to protect its S3 bucket data from accidental deletion or overwrite. Which feature should be enabled?
Easy142A 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?
Medium143Match each AWS CloudFormation concept to its description.
Medium144A company uses Amazon Route 53 to route traffic to an Application Load Balancer. They want to improve availability by routing traffic to multiple ALBs in different AWS Regions. Which routing policy should they use?
Easy145A company uses DynamoDB global tables for a multi-region application. They notice that write conflicts are occurring. Which TWO strategies can reduce write conflicts?
Hard146A company uses AWS Lambda to process messages from an SQS queue. They need to ensure that if the Lambda function fails, the message is not lost and can be processed again. Which configuration is required?
Medium147A company uses AWS CloudFormation to deploy infrastructure. During a recent deployment, the stack failed to create an Amazon RDS DB instance because of a parameter validation error. The DevOps engineer fixed the parameter and wants to resume the stack creation without recreating the resources that were already successfully created. The stack template is parameterized and uses nested stacks. What is the MOST efficient way to resume the stack creation?
Easy148A company uses Amazon DynamoDB as the database for a mobile application. The application requires single-digit millisecond read and write latency and must be resilient to the failure of an entire AWS Region. Which DynamoDB feature should the company use?
Easy149A company uses Amazon Route 53 for DNS. They want to ensure that if their primary website endpoint fails, traffic is automatically routed to a secondary endpoint in a different Region. Which routing policy should be used?
Easy150Refer to the exhibit. A DevOps engineer runs the describe-target-health command and receives the output shown. The ALB target group has two instances. One instance is healthy, and the other is unhealthy with a 502 error. What is the most likely cause of the 502 error?
Hard151A company's DevOps team is designing a disaster recovery plan for a critical application. The application runs on EC2 instances with an RDS MySQL database. The Recovery Time Objective (RTO) is 15 minutes, and the Recovery Point Objective (RPO) is 1 hour. Which approach BEST meets these requirements?
Easy152Refer to the exhibit. A DevOps engineer applies the IAM policy shown to an S3 bucket to enforce server-side encryption. However, users report that some uploads succeed without encryption. What is the most likely reason?
Easy153A company runs a critical batch processing workload on a fleet of EC2 instances in a single AWS Region. The workload can tolerate interruptions but must complete within 4 hours and must not lose progress if an instance is terminated. The company wants to minimize cost and operational overhead while ensuring resilience against a single Availability Zone failure. Which solution meets these requirements?
Medium154A company is migrating a monolithic application to a microservices architecture on AWS. To improve resilience, which THREE design patterns should be implemented? (Select THREE.)
Hard155A company runs a containerized application on Amazon ECS with Fargate launch type. The application experiences intermittent failures when the ECS service scheduler attempts to place tasks during a deployment. The DevOps engineer notices that tasks fail to start due to insufficient IP addresses in the VPC subnets. What is the MOST resilient solution to prevent this issue?
Hard156A 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?
Easy157A company wants to ensure its Amazon RDS DB instance is highly available with automatic failover in case of an AZ failure. Which configuration should they use?
Easy158A company is designing a highly available architecture for a web application that uses Amazon EC2 instances. The application must be resilient to the failure of a single instance and a single Availability Zone. Which TWO actions should the company take? (Choose TWO.)
Easy159A DevOps engineer runs the above command and sees that one target is unhealthy with reason 'Target.Timeout'. The target is an EC2 instance running a web server on port 80. The security group for the instance allows inbound traffic on port 80 from the ALB's security group. What is the most likely cause of the health check failure?
Medium160A 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?
Hard161A company is designing a multi-region active-active architecture for a stateless web application. The application uses a DynamoDB table as its data store. The company wants to minimize write latency and ensure that writes are accepted in any region with eventual consistency. Which DynamoDB feature should they use?
Easy162A company is designing a disaster recovery plan for a MySQL database running on Amazon RDS. The database is critical and must have an RPO of 5 minutes and an RTO of 1 hour. The primary Region is us-east-1, and the DR Region is us-west-2. Which TWO steps should the company take to meet these requirements? (Choose TWO.)
Hard163A company wants to ensure that its application can recover from an Amazon S3 service disruption. The application reads and writes data to S3. Which strategy should the application implement to achieve resilience?
Easy164A company is using AWS CloudFormation to deploy a critical application stack. The company wants to ensure that the stack can be recovered quickly in case of a failure. Which THREE strategies should the company implement? (Choose THREE.)
Medium165A company runs a serverless application using AWS Lambda functions that process messages from an Amazon SQS queue. The function scales up to handle high traffic but sometimes experiences throttling errors (HTTP 429) from Lambda. The company wants to improve the resilience of the application by reducing throttling. The SQS queue is configured as a Lambda event source with a batch size of 10. The Lambda function has a reserved concurrency of 100. Which combination of actions will best reduce throttling? (Choose the single best answer.)
Medium166A company is designing a resilient architecture for a web application that uses Amazon RDS for MySQL. The application must be able to withstand the loss of an entire AWS Region. Which TWO actions should the company take?
Medium167A company uses a third-party backup solution to back up its EC2 instances daily. The backups are stored in an S3 bucket with default settings. The company wants to ensure that backups are protected from accidental deletion and are available for at least one year. Which combination of S3 features should the DevOps engineer implement?
Medium168A DevOps team is designing a disaster recovery plan for a production RDS for PostgreSQL database. The RPO must be less than 5 minutes and the RTO less than 1 hour. The database size is 2 TB. Which solution is MOST cost-effective?
Medium169A company runs a critical web application on Amazon EC2 instances behind an Application Load Balancer (ALB) across multiple Availability Zones. The application stores session data in a shared Amazon ElastiCache for Redis cluster. The operations team reports that during a recent AZ failure, users experienced session loss and application errors. Which combination of actions should the company take to improve resilience and maintain session state during an AZ failure? (Choose TWO.)
Medium170A company runs a stateful application on EC2 instances. The application stores session data locally. The instances are behind an ALB with sticky sessions enabled. A scaling event terminates an instance, causing loss of session data. How can the company prevent this while maintaining performance?
Medium171A company is building a multi-tier web application on AWS. The application must be resilient to the failure of an entire Availability Zone. The architecture includes an Application Load Balancer (ALB), EC2 instances in an Auto Scaling group, and an Amazon RDS for MySQL database. Which TWO actions should be taken to achieve this resilience? (Choose two.)
Medium172A company runs a microservices architecture on Amazon ECS. They want to ensure that if a service fails, it does not cascade to other services. Which TWO design patterns should they implement?
Hard173A 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?
Hard174A company uses Amazon Route 53 for DNS and wants to ensure high availability for a web application hosted on two EC2 instances in different Availability Zones. The application uses an Application Load Balancer. What is the simplest way to achieve resilience if one Availability Zone becomes unavailable?
Easy175A 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?
Easy176A company runs a containerized microservices application on Amazon EKS. The application includes a critical service that processes real-time financial transactions. This service must be highly available and resilient to node failures. The current setup uses a Deployment with 3 replicas and a ClusterIP service. During a recent node failure, the application experienced a brief period of unavailability. Which action should the DevOps engineer take to improve resilience without changing the underlying infrastructure?
Hard177A company runs a critical application on Amazon EC2 instances in an Auto Scaling group. The application generates logs that are sent to Amazon CloudWatch Logs. The DevOps team needs to configure a metric filter to monitor for error patterns and trigger an alarm when the error rate exceeds 5% of total requests over a 5-minute period. Which TWO steps should the team take? (Choose TWO.)
Hard178Drag and drop the steps to perform a disaster recovery failover from a primary region to a secondary region using AWS Route 53 and RDS.
Medium179A company is designing a resilient architecture for a web application using AWS Global Accelerator and two Application Load Balancers in different AWS Regions. The application is stateless and uses a global DynamoDB table for data. What is the primary benefit of using Global Accelerator in this architecture?
Easy180A company uses AWS Lambda with Amazon DynamoDB to process orders. During peak hours, the Lambda function sometimes fails with throttling errors from DynamoDB. The system must be resilient and cost-effective. What should a DevOps engineer do?
Hard181A DevOps engineer needs to ensure that an application running on EC2 can automatically recover from an underlying hardware failure without manual intervention. Which AWS feature should be enabled?
Easy182A company has a production environment that uses Amazon Route 53 for DNS and an Application Load Balancer (ALB) to distribute traffic to EC2 instances. The company wants to implement a disaster recovery plan that automatically fails over to a secondary region in case the primary region becomes unavailable. Which configuration should be used?
Medium183A company runs a critical web application on EC2 instances behind an Application Load Balancer. To improve resilience, they want to automatically replace failed instances. Which AWS service should they use?
Medium184A 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?
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Frequently asked questions
- What does the Resilient Cloud Solutions domain cover on the DOP-C02 exam?
- You must be able to select the right resilience mechanism per scenario: Multi-AZ for high availability, multi-Region for disaster recovery, Auto Scaling for elasticity, and managed replication for data stores. The single most important thing is matching the failure scope (AZ vs Region vs instance) to the correct AWS feature.
- How many questions are in this domain?
- This page lists all 184 Resilient Cloud Solutions questions in the DOP-C02 question bank. The actual exam draws from this domain proportionally to its weighting in the official exam blueprint.
- What is the best way to practise this domain?
- Start with a short focused session (10 questions) to identify gaps, then work through explanations. Repeat with a longer session once the weak areas feel solid.
- Can I practise only Resilient Cloud Solutions questions?
- Yes — the session launcher on this page filters questions to this domain only. Choose any session length for inline explanations and scoring.