DOP-C02 Resilient Cloud Solutions Practice Test 16 — 15 Questions

Question 1

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

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

Accepted Answer

Configure Amazon RDS Proxy in front of the RDS instance.. Amazon RDS Proxy reduces failover time by pooling and reusing connections, allowing the application to resume quickly after failover without waiting for new connections to be established. Option E is correct because setting the DNS TTL for the RDS endpoint to 1 second ensures that the client DNS cache expires quickly, so the application can reconnect to the new primary IP address promptly after failover. Option A (Performance Insights) is for monitoring, not failover. Option C (synchronous replication) is already used by Multi-AZ and does not affect failover time. Option D (increasing instance size) improves performance but does not reduce failover duration.

Answer

Enable Performance Insights to monitor database load.

Answer

Use synchronous replication to the standby instance.

Answer

Increase the DB instance class to a larger size.

Question 2

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

Accepted Answer

Enable AWS Backup for the EFS file system with daily backups.. The correct actions are to enable AWS Backup for daily backups (Option B) and recreate the EFS file system as a Regional (Standard) file system (Option D). AWS Backup provides additional durability and point-in-time recovery, while Regional EFS automatically replicates data across multiple Availability Zones, ensuring availability even if one AZ fails. Option A (increasing throughput) does not address durability. Option C (copying to S3) is possible but not a primary solution and changes architecture. Option E (mounting from multiple AZs) is only possible with Regional EFS, but with One Zone it's not supported.

Answer

Increase the EFS throughput mode to Provisioned.

Answer

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

Answer

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

Question 3

A 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.)

Accepted Answer

Switch the Elastic Beanstalk environment to a load-balanced, auto-scaled environment with a minimum of 2 instances across 2 Availability Zones.. Switching to a load-balanced, auto-scaled environment with a minimum of 2 instances across 2 Availability Zones improves availability and resilience by distributing traffic and providing failover capacity. Option D is correct because enabling Multi-AZ for RDS provides a standby replica in a different Availability Zone, ensuring automatic failover and high availability for the database. Option E is correct because Amazon RDS Proxy manages database connections efficiently, reducing connection overhead and improving scalability during traffic spikes. Option A (ElastiCache) is an additional cost that may not be necessary if caching is not a primary concern; the focus should be on core resilience first. Option B (dedicated instances) adds unnecessary cost and does not directly address high availability or resilience.

Answer

Add an Amazon ElastiCache cluster to cache frequent database queries.

Answer

Use dedicated instances for the EC2 instances to ensure consistent performance.

Question 4

A company runs a critical application on AWS Lambda functions that process real-time streaming data from Amazon Kinesis Data Streams. Each Lambda function processes a batch of records and writes results to an Amazon DynamoDB table. The application is sensitive to data loss and requires exactly-once processing semantics. Recently, the operations team observed that the Lambda function is failing intermittently with 'ProvisionedThroughputExceededException' errors from DynamoDB. The Lambda function's batch size is 100, and the function is configured with a reserved concurrency of 500. The DynamoDB table has 100 read capacity units (RCUs) and 100 write capacity units (WCUs) with auto scaling enabled up to 1000 WCUs. The function's execution role has the necessary DynamoDB permissions. The Kinesis stream has 10 shards. The DevOps engineer needs to resolve the throttling errors without losing data. Which combination of actions should the engineer take? (Choose THREE.)

Accepted Answer

Set the Lambda function's batch size to a lower value (e.g., 10) and enable parallelization factor per shard.. Reducing the batch size decreases the number of records processed per invocation, lowering the write load on DynamoDB. Note that enabling the parallelization factor per shard increases the number of concurrent invocations per shard, which could actually increase write pressure; therefore, if used, it must be accompanied by sufficient write capacity. Option C is correct because configuring the event source mapping to retry failed records ensures that records are not lost; the Lambda function can retry after throttling errors, supporting exactly-once semantics. Option E is correct because increasing the DynamoDB table's maximum write capacity auto scaling limit allows the table to scale to higher WCUs during bursts, reducing ProvisionedThroughputExceededExceptions. Option B is incorrect because the error is due to write capacity, not read capacity; increasing RCUs does not help. Option D is incorrect because increasing reserved concurrency would increase the number of concurrent Lambda invocations, potentially increasing writes and worsening throttling.

Answer

Increase the DynamoDB table's read capacity units to 1000.

Answer

Increase the Lambda function's reserved concurrency to 1000.

Question 5

A company uses Amazon RDS Multi-AZ for disaster recovery. The primary DB instance in us-east-1a fails. What happens next?

Accepted Answer

The standby DB instance in us-east-1b is promoted automatically and the CNAME record is updated. RDS Multi-AZ automatically fails over to the standby in a different Availability Zone within minutes. The CNAME record is updated to point to the standby DB instance, so no manual intervention is needed. Option A is correct because this automatic failover and CNAME update occurs. Option B is wrong because no manual promotion is required. Option C is wrong because the primary is not rebuilt in the same AZ; it fails over to a standby in a different AZ. Option D is wrong because read replicas are not used for Multi-AZ failover; a standby instance is promoted.

Answer

The administrator must manually promote the standby instance

Answer

The primary instance is automatically rebuilt in the same AZ

Answer

A read replica in us-east-1b is automatically promoted to primary

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 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 8

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 9

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 10

A 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?

Accepted Answer

Migrate session state to ElastiCache for Redis.. Migrating session state from in-memory EC2 instance storage to ElastiCache for Redis decouples session data from individual instances. This ensures that when a new deployment replaces instances, sessions persist independently, preventing timeouts and errors. ElastiCache provides a centralized, highly available session store that survives instance termination and scaling events.

Answer

Enable sticky sessions (session affinity) on the ALB.

Answer

Increase the ALB idle timeout to 600 seconds.

Answer

Increase the EC2 instance size to handle higher memory.

Question 11

A 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.)

Accepted Answer

Configure Route 53 with a failover routing policy to direct traffic to the secondary Region if the primary fails.. Amazon Route 53 with a failover routing policy allows the company to route traffic to a secondary Region when health checks detect a failure in the primary Region. This provides DNS-level failover, which is a fundamental component of multi-Region resilience for HTTP-based applications.

Answer

Use Amazon CloudFront with multiple origins pointing to each Region's API Gateway.

Answer

Deploy Lambda@Edge functions to handle requests at edge locations.

Question 12

Which TWO strategies can be used to improve the resilience of an application running on Amazon ECS with Fargate? (Select TWO.)

Accepted Answer

Configure the ECS service to place tasks in multiple Availability Zones.. Configuring the ECS service to place tasks in multiple Availability Zones distributes the application across physically separate data centers, so if one AZ fails, the tasks in other AZs continue to run. Option D is correct because implementing a circuit breaker pattern for downstream dependencies prevents cascading failures by detecting faults and failing fast, allowing the system to recover gracefully. Option A is incorrect; using a single subnet for all tasks typically places them in a single Availability Zone, reducing fault tolerance. Option C is incorrect; increasing task memory reservation helps handle peak load but does not improve resilience against failures. Option E is incorrect; scheduled scaling adjusts capacity based on historical patterns and does not handle unexpected spikes or failures.

Answer

Use a single subnet for all tasks to simplify networking.

Answer

Increase the task memory reservation to handle peak load.

Answer

Use scheduled scaling to adjust task count based on historical patterns.

Question 13

Which THREE components are required to implement a global application that can withstand the failure of an entire AWS Region? (Select THREE.)

Accepted Answer

Amazon CloudFront with multiple origins and origin failover.. To implement a global application resilient to an entire AWS Region failure, you need DNS failover, multi-region data replication, and edge caching with origin failover. Amazon Route 53 with health checks and failover routing policy (E) detects region outages and directs traffic to healthy regions. Amazon CloudFront with multiple origins and origin failover (B) provides edge caching and can switch to a secondary origin if the primary fails. Amazon DynamoDB Global Tables (C) replicates data across regions for multi-region writes and reads. Option A (ALB in primary region) is regional and cannot handle cross-region failover. Option D (RDS Single-AZ) lacks multi-region replication and is not resilient.

Answer

An Application Load Balancer in the primary Region.

Answer

Amazon RDS with a single-AZ deployment.

Question 14

A 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?

Accepted Answer

Existing connections are dropped, and applications must reconnect to the new primary using the same endpoint.. During a Multi-AZ failover, RDS automatically updates the DNS record to point to the standby, but existing connections to the primary are dropped and must be re-established. Option A is wrong because connections are not preserved. Option B is wrong because Multi-AZ automatically fails over without manual promotion. Option D is wrong because the CNAME record does not change; it's a DNS update.

Answer

Existing connections are automatically redirected to the standby without interruption.

Answer

The RDS endpoint IP address changes, and the application must update its configuration.

Answer

The primary DB instance is promoted to standby and connections remain active.

Question 15

A company runs a critical application on Amazon ECS with Fargate launch type. The application is deployed across multiple Availability Zones. The DevOps team needs to ensure that if an entire Availability Zone fails, the application continues to serve traffic without manual intervention. What should the team do?

Accepted Answer

Configure the ECS service to run tasks in at least two Availability Zones and enable the ECS service auto-recovery feature.. The ECS service's AZ rebalancing feature automatically redistributes tasks across Availability Zones when an imbalance is detected, such as after an AZ failure. By configuring the service to run tasks in at least two AZs and enabling this feature, the ECS service will automatically launch replacement tasks in the remaining healthy AZs to maintain the desired count, ensuring continued traffic serving without manual intervention.

Answer

Use an Amazon ECS service auto-scaling policy to automatically replace tasks in the failed AZ.

Answer

Configure the ALB to enable cross-zone load balancing and enable the ECS service's AZ rebalancing feature.

Answer

Set the ECS service's minimum healthy percent to 100 and maximum percent to 200.