SOA-C02 Reliability and Business Continuity Practice Test 10 — 15 Questions

Question 1

A company runs a web application on EC2 instances in an Auto Scaling group behind an Application Load Balancer. The application stores session data in an in-memory cache on the EC2 instances. During an instance refresh, users lose their session data. Which action should be taken to improve reliability without major application changes?

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

Accepted Answer

Move session state to Amazon ElastiCache for Redis.. Amazon ElastiCache for Redis provides a fully managed, external, and highly available in-memory data store that can be used to persist session state outside of the EC2 instances. By moving session data to Redis, the session state survives instance refreshes, terminations, or scaling events without requiring any changes to the application's session management logic beyond pointing to the Redis endpoint. This decouples session state from the compute layer, ensuring reliability and data durability during Auto Scaling lifecycle events.

Answer

Use ElastiCache for Memcached with auto-discovery.

Answer

Increase the minimum size of the Auto Scaling group.

Answer

Enable sticky sessions (session affinity) on the ALB target group.

Question 2

A company runs a production RDS for PostgreSQL instance with Multi-AZ enabled. The database experiences a failover due to an AZ outage. After the failover, the application experiences high latency on write operations. What is the most likely cause?

Accepted Answer

Synchronous replication to the standby instance in the other AZ is causing additional latency.. With Multi-AZ enabled, RDS for PostgreSQL uses synchronous replication to the standby instance in a different Availability Zone. After a failover, the new primary continues to use synchronous replication to the new standby, which adds latency to write operations because each write must be acknowledged by the standby before the primary commits. This synchronous replication overhead is the most likely cause of the increased write latency.

Answer

The application is now reading from the standby instance, which has higher read latency.

Answer

The failover switched to a read replica in a different AZ.

Answer

The failover switched to asynchronous replication mode.

Question 3

A SysOps administrator is designing a disaster recovery plan for a critical application that runs on EC2 instances with data stored on EBS volumes. The application requires an RPO of 15 minutes and an RTO of 2 hours. The current solution uses EBS snapshots taken every 6 hours. The administrator needs to improve the backup strategy to meet the RPO. What is the most cost-effective way to achieve this?

Accepted Answer

Increase the snapshot frequency to every 15 minutes.. Increasing the snapshot frequency to every 15 minutes directly reduces the recovery point objective (RPO) from 6 hours to 15 minutes, meeting the requirement without incurring additional infrastructure costs. EBS snapshots are incremental and cost-effective, as only changed blocks are stored after the initial snapshot, making frequent snapshots a practical approach for achieving a low RPO.

Answer

Enable EBS Recycle Bin with a retention rule of 15 minutes.

Answer

Change the EBS volume type to io2 Block Express.

Answer

Use EBS Multi-Attach to attach volumes to multiple instances for redundancy.

Question 4

A company runs a stateless web application on EC2 instances in an Auto Scaling group. The instances are behind an Application Load Balancer. The Auto Scaling group uses a dynamic scaling policy based on average CPU utilization. During a traffic spike, new instances are launched but take 5 minutes to become healthy. Users experience errors during this time. Which solution would reduce the time to serve traffic from new instances?

Accepted Answer

Use a launch template with a pre-provisioned AMI.. A pre-provisioned AMI eliminates the need for software installation and configuration at launch time, reducing the time for new EC2 instances to become healthy. By baking the application and dependencies into the AMI, instances can start serving traffic almost immediately after booting, rather than waiting for user data scripts or configuration management tools to complete.

Answer

Add a lifecycle hook to delay instance termination.

Answer

Increase the cooldown period for the scaling policy.

Answer

Use a larger instance type.

Question 5

An organization is using AWS CloudFormation to deploy infrastructure. The SysOps administrator needs to ensure that if a stack update fails, the stack automatically rolls back to the last known good state. Which stack update option should be configured?

Accepted Answer

Rollback on failure. CloudFormation's 'Rollback on failure' option, enabled by default, automatically reverts a stack to its last known good state if a stack update fails. This ensures that failed updates do not leave the infrastructure in an inconsistent or partially deployed state, maintaining reliability and business continuity.

Answer

Disable rollback

Answer

Change sets

Answer

Stack policy

Question 6

A company runs a critical database on an EC2 instance with an EBS volume. The administrator wants to create a disaster recovery plan that can recover the database in a different AWS Region within 4 hours. The database size is 1 TB. What is the MOST efficient approach to meet the RTO?

Accepted Answer

Copy the AMI and underlying EBS snapshots to the DR region.. Copying the AMI and its underlying EBS snapshots to the DR region creates a fully independent, bootable image that can be launched as an EC2 instance in the target region. This approach directly supports the 4-hour RTO by allowing the administrator to pre-stage the AMI copy or initiate the copy on-demand, and then launch the instance from the copied AMI without needing to recreate the volume from individual snapshots or reconfigure instance metadata.

Answer

Share the AMI with the target region.

Answer

Use EBS snapshots directly in the DR region.

Answer

Configure AWS Backup to copy backups to the DR region.

Question 7

A company uses AWS CloudTrail to log API activity. The SysOps administrator needs to ensure that log files are protected from accidental deletion and are available for compliance audits for at least 7 years. Which service should be used to meet these requirements?

Accepted Answer

Enable S3 Object Lock in Compliance mode.. S3 Object Lock in Compliance mode provides a write-once-read-many (WORM) model that prevents any user, including the AWS account root user, from deleting or overwriting objects for the specified retention period. This meets both the protection from accidental deletion and the 7-year compliance audit requirement, as the retention mode cannot be shortened or removed once applied.

Answer

Enable S3 Versioning on the CloudTrail S3 bucket.

Answer

Move CloudTrail logs to Amazon S3 Glacier after 90 days.

Answer

Store logs in Amazon CloudWatch Logs with an expiration policy of 7 years.

Question 8

An application running on Amazon ECS with Fargate launch type is experiencing intermittent failures. The tasks are spread across multiple Availability Zones. The SysOps administrator notices that failures occur only when an entire AZ becomes unavailable. What should the administrator do to improve the reliability of the application?

Accepted Answer

Increase the desired task count to ensure sufficient capacity across AZs.. Increasing the desired task count ensures that ECS Fargate tasks are distributed across multiple Availability Zones, providing sufficient capacity to absorb the loss of an entire AZ. When one AZ becomes unavailable, the remaining tasks in other AZs continue to serve traffic, improving application reliability. This approach leverages the multi-AZ architecture already in place by ensuring enough tasks are running to handle the load even after an AZ failure.

Answer

Use multiple subnets in the same AZ.

Answer

Use a cluster placement group.

Answer

Attach an Amazon EFS filesystem to all tasks.

Question 9

Which TWO actions should a SysOps administrator take to ensure high availability of a web application running on EC2 instances? (Choose two.)

Accepted Answer

Configure an Auto Scaling group with a health check to replace unhealthy instances.. Option D is correct because an Auto Scaling group with health checks (EC2 status checks and optionally ELB health checks) automatically detects and replaces unhealthy instances, maintaining the desired capacity and thus high availability. Option E is correct because deploying EC2 instances across multiple Availability Zones ensures the application survives an AZ-level failure, since each AZ has independent power, cooling, and networking. Option A is incorrect because termination protection only prevents accidental instance termination; it does not improve availability or recover failed instances. Option B is incorrect because placing all instances in a single AZ creates a single point of failure, reducing availability. Option C is incorrect because a larger instance type only increases capacity, not redundancy or fault tolerance.

Answer

Enable termination protection on all EC2 instances.

Answer

Launch all EC2 instances in a single Availability Zone.

Answer

Use a larger instance type for all EC2 instances.

Question 10

Which TWO steps should a SysOps administrator take to ensure data durability for an Amazon S3 bucket that stores critical documents? (Choose two.)

Accepted Answer

Enable S3 Versioning.. S3 Versioning (B) protects against accidental deletion and overwrites by preserving every version of an object, including deletions as delete markers. This ensures data durability by allowing recovery of previous versions. Cross-Region Replication (E) provides durability by asynchronously replicating objects to a different AWS region, protecting against region-wide failures.

Answer

Enable default encryption with SSE-S3.

Answer

Use S3 Transfer Acceleration.

Answer

Enable MFA Delete.

Question 11

A company runs a web application on EC2 instances in an Auto Scaling group behind an Application Load Balancer. The application stores session data in an in-memory cache on the EC2 instances. During an instance refresh, users lose their session data. Which action should be taken to improve reliability without major application changes?

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

Accepted Answer

Enable DNS caching with a low TTL in the application and use the RDS instance endpoint with a retry mechanism.. During an RDS Multi-AZ failover, the DNS record for the primary instance endpoint is updated to point to the standby instance. If the application caches the old DNS resolution with a high TTL, it continues to send connections to the unreachable primary, causing 5xx errors. Enabling DNS caching with a low TTL (e.g., 5 seconds) and implementing a retry mechanism ensures the application quickly resolves the new endpoint and reconnects, minimizing downtime.

Answer

Configure the application to use the RDS reader endpoint.

Answer

Use a read replica to offload read traffic and reduce failover impact.

Answer

Increase the database connection pool size to handle retries.

Question 12

A company uses AWS Backup to back up its Amazon EFS file system daily. The backup retention policy is set to 30 days. Recently, a user accidentally deleted a critical directory. The company wants to restore the directory as it existed 2 days ago. What is the MOST cost-effective and quickest way to achieve this?

Accepted Answer

Restore the backup from 2 days ago to a new EFS file system, then copy the directory to the original file system.. AWS Backup creates point-in-time snapshots of EFS file systems. Restoring a backup from 2 days ago to a new EFS file system allows you to mount that new file system, copy the specific directory back to the original file system, and then delete the temporary file system. This is the most cost-effective and quickest approach since it avoids moving data to on-premises servers and uses native AWS services without additional replication costs.

Answer

Use the EFS console to recover the directory from the .Trash folder.

Answer

Enable EFS replication to another region and then fail back.

Answer

Use AWS Backup to restore the entire file system to an on-premises server, then copy the directory back.

Question 13

A SysOps administrator needs to ensure that an Amazon S3 bucket can withstand the loss of an entire AWS Availability Zone. What is the SIMPLEST configuration to meet this requirement?

Accepted Answer

Use S3 Standard storage class.. S3 Standard automatically stores objects across a minimum of three Availability Zones (AZs) within the same AWS Region. This design ensures that the bucket can withstand the loss of an entire AZ without any additional configuration, making it the simplest option to meet the requirement.

Answer

Enable cross-region replication to a bucket in another Region.

Answer

Use S3 One Zone-IA storage class.

Answer

Enable MFA Delete on the bucket.

Question 14

A company runs a stateless web application on EC2 instances in an Auto Scaling group across multiple Availability Zones. The application experiences increased latency during peak hours. The SysOps administrator needs to improve the application's performance and reliability. Which action should be taken?

Accepted Answer

Increase the maximum instance count in the Auto Scaling group.. Increasing the maximum instance count allows the Auto Scaling group to launch more EC2 instances during peak hours, distributing the load across more resources and reducing latency. This directly improves both performance (by handling more requests) and reliability (by maintaining capacity under increased demand).

Answer

Use larger EC2 instance types instead of smaller ones.

Answer

Reduce the Auto Scaling group's cooldown period to scale out faster.

Answer

Change the scaling metric from CPU utilization to memory utilization.

Question 15

A company has a production RDS for PostgreSQL instance with Multi-AZ enabled. During a recent failover test, the application experienced a 5-minute downtime. The company requires that failover be completed within 2 minutes. Which action should be taken to meet this requirement?

Accepted Answer

Configure an RDS Proxy in front of the database.. RDS Proxy reduces failover time by maintaining database connections and connection pooling, allowing the application to reconnect quickly without waiting for DNS propagation or new connection setup. In a Multi-AZ failover, RDS Proxy can typically complete failover in under 60 seconds, meeting the 2-minute requirement by minimizing connection disruption.

Answer

Migrate the database to Amazon Aurora with Multi-AZ.

Answer

Enable automated backups with a short retention period.

Answer

Increase the DB instance class to a larger size.