SOA-C02 Reliability and Business Continuity Practice Test 2 — 15 Questions

Question 1

A company runs a stateless web application on EC2 instances in an Auto Scaling group. The application is deployed in us-east-1 with three Availability Zones. The SysOps administrator wants to ensure that the application remains available even if an entire Availability Zone becomes unavailable. The Auto Scaling group is configured with a minimum of 3, maximum of 9, and desired capacity of 3. The instances are distributed evenly across the three AZs. What additional configuration is required to ensure the application can survive an AZ failure?

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

Accepted Answer

Ensure the load balancer is cross-zone load balancing enabled and the Auto Scaling group has a sufficient maximum size to handle the load of a failed AZ.. For an ASG spread across three AZs with desired capacity 3, an AZ failure removes one instance, leaving two. To survive, the ASG must be able to launch replacement capacity in the surviving AZs, which requires the maximum size to be large enough (at least 6, since the surviving two AZs must absorb the third AZ's share). Additionally, the load balancer must have cross-zone load balancing enabled so traffic is redistributed to healthy instances in the remaining AZs rather than being pinned to the failed AZ's targets.

Answer

Increase the desired capacity to 6 to ensure enough capacity if one AZ fails.

Answer

Configure the Auto Scaling group to launch instances in only two AZs to reduce costs.

Answer

Place the Auto Scaling group in a single AZ to simplify management.

Question 2

A company runs a web application on AWS that uses an Application Load Balancer (ALB) across multiple Availability Zones. The application is deployed on EC2 instances in an Auto Scaling group behind the ALB. The RDS database is Multi-AZ with synchronous replication. Recently, the operations team noticed that during a planned failover test of the primary RDS instance, the application experienced a 30-second timeout and returned 503 errors to users. The RDS failover completed successfully, but the application did not recover until the Auto Scaling group replaced all instances. The application health check endpoint on the EC2 instances checks database connectivity. The ALB health check is configured to check the health check endpoint every 10 seconds with a threshold of 2 consecutive failures. The application uses a connection pool with a timeout of 5 seconds. What is the MOST likely cause of the 503 errors and the need to replace instances?

Accepted Answer

The EC2 instances are caching the RDS DNS name, causing them to connect to the old primary endpoint after failover. The application health check fails, leading to instance replacement.. During an RDS Multi-AZ failover, the DNS CNAME for the primary endpoint is updated to point to the standby, but EC2 instances with long-lived connections or DNS caching may continue resolving to the old IP. The application's health check endpoint checks database connectivity, so when it fails, the ALB marks instances unhealthy and the Auto Scaling group replaces them. This matches the observed 30-second timeout and instance replacement.

Answer

The ALB health check threshold of 2 consecutive failures is too low, causing premature instance replacement.

Answer

The application connection pool timeout of 5 seconds is too short for RDS failover.

Answer

The Multi-AZ RDS configuration is insufficient; the company should implement a warm standby database in another Region.

Question 3

A company stores critical data in an S3 bucket. The SysOps administrator needs to ensure that the data is durable and can be recovered if an entire AWS Region becomes unavailable. What is the MOST cost-effective solution?

Accepted Answer

Configure S3 Cross-Region Replication to a bucket in another Region.. D is correct because S3 Cross-Region Replication (CRR) automatically replicates objects to a bucket in another AWS Region, ensuring data durability and recoverability even if an entire Region becomes unavailable. This is the most cost-effective solution for cross-region disaster recovery as it only incurs replication costs and storage fees in the destination Region, without requiring manual intervention or additional infrastructure.

Answer

Use AWS Backup to manually copy the bucket to another Region.

Answer

Enable S3 Versioning on the bucket.

Answer

Use S3 Standard storage class.

Question 4

A company runs a web application on EC2 instances behind an Application Load Balancer. The application stores session data in a DynamoDB table. To improve reliability, the SysOps administrator needs to ensure that session data is preserved if an EC2 instance fails. Which action should the administrator take?

Accepted Answer

Use DynamoDB to store session data, making it accessible from any instance.. The application already stores session data in DynamoDB, which is a fully managed, highly available, and durable database service. By using DynamoDB, session data is persisted independently of any single EC2 instance, so if an instance fails, another instance can retrieve the same session data from DynamoDB without loss. This design ensures session data is preserved and accessible from any healthy instance, meeting the reliability requirement.

Answer

Enable sticky sessions (session affinity) on the ALB.

Answer

Mount the same EBS volume to all EC2 instances to share session data.

Answer

Store session data in an ElastiCache Memcached cluster.

Question 5

A company has a critical application running on EC2 instances in an Auto Scaling group behind an ALB. The application uses a custom health check endpoint at /health. The SysOps administrator notices that the ALB occasionally marks instances as unhealthy even though the application is running correctly. The health check settings are: HealthCheckIntervalSeconds=30, HealthyThresholdCount=5, UnhealthyThresholdCount=2. What is the most likely cause of the intermittent health check failures?

Accepted Answer

The HealthyThresholdCount is set too high, causing instances to remain unhealthy after transient issues.. With HealthyThresholdCount=5, an instance must pass five consecutive health checks to be marked healthy. After a transient failure, the instance requires five successful checks to become healthy again, which can cause prolonged unhealthy periods. Option A is incorrect because if the health check endpoint returns 5xx errors, the ALB would mark the instance as unhealthy; these errors are not ignored. Option B is incorrect because an UnhealthyThresholdCount of 2 is standard and does not cause intermittent failures. Option D is incorrect because using TCP instead of HTTP would not cause intermittent failures if the instance is reachable; the issue is related to the healthy threshold, not the protocol.

Answer

The health check endpoint returns 5xx errors, which are ignored by the ALB.

Answer

The UnhealthyThresholdCount is set too low.

Answer

The health check is using TCP instead of HTTP.

Question 6

A SysOps administrator is tuning the health check of an Auto Scaling group. The group uses an ALB. The application takes up to 2 minutes to start. The health check settings are: HealthCheckGracePeriod=300, HealthCheckType=EC2. The administrator notices that instances are often marked unhealthy and terminated shortly after launch. What should the administrator change?

Accepted Answer

Change the HealthCheckType to ELB.. Change the HealthCheckType to ELB. With EC2 type, the ASG only uses EC2 status checks and ignores the ALB health check, so ALB health check failures would not directly cause termination. Setting HealthCheckType=ELB makes the ASG use the ALB health check results, and the HealthCheckGracePeriod (300 seconds) then applies to those results, delaying termination until the application has time to start. Increasing the grace period (B) would not help because the ALB health check is not used when HealthCheckType=EC2; decreasing it (D) would make the problem worse. Option C is the correct answer.

Answer

Change the HealthCheckType to EC2 (already EC2, but change to ELB).

Answer

Increase the HealthCheckGracePeriod to 600 seconds.

Answer

Decrease the HealthCheckGracePeriod to 120 seconds.

Question 7

An application runs on EC2 instances in an Auto Scaling group. The instances process messages from an SQS queue. To ensure high availability, the SysOps administrator has configured the Auto Scaling group to span three Availability Zones. However, during a recent failure of one AZ, the application experienced a temporary increase in processing latency. What is the MOST likely cause of this latency?

Accepted Answer

SQS messages in the failed AZ are temporarily unavailable until they are replicated to other AZs.. SQS stores messages redundantly across multiple AZs within a region, but when an AZ fails, messages that were in-flight or stored in that AZ become temporarily unavailable until the SQS service completes its internal replication and recovery processes. This transient unavailability causes a spike in processing latency because the application cannot retrieve those messages until they are replicated to healthy AZs. The latency resolves once SQS finishes replicating the messages to the remaining AZs.

Answer

The SQS queue is configured to use a single AZ for message storage.

Answer

The application is not configured to process messages from multiple AZs.

Answer

The Auto Scaling group's minimum size is too low to handle the load after the AZ failure.

Question 8

A company uses Amazon Route 53 for DNS and wants to ensure that its web application is highly available across two AWS Regions. The application runs behind an Application Load Balancer in each Region. Which routing policy should be used?

Accepted Answer

Failover routing policy. The failover routing policy in Amazon Route 53 is designed to route traffic to a primary resource (e.g., an Application Load Balancer in one AWS Region) and automatically redirect to a secondary resource (e.g., an ALB in another Region) if the primary becomes unhealthy. This ensures high availability across two Regions by using health checks to detect failures and perform DNS failover, which directly meets the requirement for multi-Region redundancy.

Answer

Weighted routing policy

Answer

Geolocation routing policy

Answer

Latency routing policy

Question 9

A company's S3 bucket contains critical data. The bucket policy allows s3:PutObject and s3:GetObject for all authenticated users in the account. A SysOps administrator needs to ensure that if the bucket is accidentally deleted, the objects can be recovered. Which solution meets this requirement?

Accepted Answer

Enable cross-region replication on the bucket.. Cross-region replication (CRR) automatically replicates objects to a destination bucket in a different AWS Region. If the source bucket is accidentally deleted, the replicated objects remain in the destination bucket, allowing recovery. Versioning with MFA delete (Option C) protects against accidental deletion of object versions within the bucket but does not protect against deletion of the bucket itself; when the bucket is deleted, all objects and versions are permanently lost. Options A and B are incorrect: MFA for DeleteObject only adds a security control for deleting objects, not for bucket deletion; denying s3:DeleteBucket does prevent the bucket from being deleted but does not help recover objects if deletion occurs.

Answer

Set a bucket policy that requires MFA for any s3:DeleteObject action.

Answer

Add a bucket policy that denies s3:DeleteBucket for all principals.

Answer

Enable versioning on the bucket and enable MFA delete.

Question 10

A company's critical application uses an EBS-backed EC2 instance. They want to back up the instance daily with a retention policy of 30 days. What is the MOST efficient way to achieve this?

Accepted Answer

Use Amazon Data Lifecycle Manager (DLM) to schedule EBS snapshots with a 30-day retention.. Amazon Data Lifecycle Manager (DLM) is the most efficient choice because it is a fully managed service designed specifically for automating the creation, retention, and deletion of EBS snapshots. It natively supports scheduling daily snapshots with a retention policy of 30 days without requiring custom scripts or additional services, minimizing operational overhead and cost.

Answer

Use AWS Backup to schedule EBS snapshots and set the retention policy.

Answer

Schedule a Lambda function to create an EBS snapshot daily and delete snapshots older than 30 days.

Answer

Create an AMI daily using AWS Backup and set the retention to 30 days.

Question 11

Which TWO steps should a SysOps administrator take to ensure that an RDS for MySQL instance can withstand an Availability Zone failure? (Choose 2)

Accepted Answer

Enable Multi-AZ deployment.. To withstand an Availability Zone failure, the RDS instance must provide automatic failover to a standby in a different AZ. Only Multi-AZ deployment (Option A) achieves this by provisioning a synchronous standby replica and enabling automatic failover. Automated backups (Option C) are for point-in-time recovery, not high availability, so they do not help during an ongoing AZ failure.

Answer

Create a read replica in a different AZ.

Answer

Enable automated backups with a short retention period.

Answer

Enable deletion protection on the DB instance.

Answer

Enable provisioned IOPS for the DB instance.

Question 12

Refer to the exhibit. An IAM policy is attached to an IAM user. Which action can the user perform?

Accepted Answer

Stop an EC2 instance.. The IAM policy grants the ec2:StopInstances action, which allows the user to stop EC2 instances. The condition restricts the action to instances with a specific tag, but the core permission is for stopping instances, making option C correct.

Answer

Start an EC2 instance.

Answer

Describe EC2 instances.

Answer

Terminate an EC2 instance.

Question 13

A company uses AWS CloudFormation to deploy infrastructure. They want to ensure that if a stack update fails, the stack automatically rolls back to the last known good state. Which CloudFormation stack policy should be used?

Accepted Answer

Use the default 'Rollback on failure' setting.. The default 'Rollback on failure' setting in AWS CloudFormation automatically triggers a stack rollback to the last known good state when a stack update fails. This is the built-in behavior that ensures reliability by reverting changes if an error occurs during the update process.

Answer

Enable termination protection on the stack.

Answer

Use a stack policy that prevents specific resources from being updated.

Answer

Set 'DisableRollback' to false.

Question 14

A company is designing a disaster recovery strategy for its primary AWS region. The application runs on EC2 instances with an RDS database. The RPO is 15 minutes and RTO is 2 hours. Which TWO actions should the SysOps Administrator take to meet these requirements? (Choose TWO.)

Accepted Answer

Configure RDS cross-region replication to a second region.. Option B is correct because RDS cross-region read replicas continuously replicate data asynchronously to a second region, which can keep the replica lag well within the 15-minute RPO and can be promoted to a standalone primary in minutes, satisfying the 2-hour RTO. Option E is correct because storing CloudFormation templates in an S3 bucket with Cross-Region Replication ensures the infrastructure-as-code definitions are available in the DR region, enabling rapid, consistent re-provisioning of the EC2 and supporting resources within the RTO. Option A is not correct because AMIs alone do not provide continuous data replication for the RDS database and would not meet the 15-minute RPO without an accompanying database strategy. Option C is not correct because manual snapshots every 15 minutes are operationally unreliable, and RDS snapshot copy times can exceed the RPO/RTO window. Option D is not correct because daily AWS Backup copies cannot achieve a 15-minute RPO.

Answer

Create AMIs of the EC2 instances and share them with the DR region.

Answer

Take manual RDS snapshots every 15 minutes and copy them to the DR region.

Answer

Use AWS Backup to copy backups to a second region daily.

Question 15

A company wants to ensure its SysOps Administrator can recover an EBS volume from a snapshot. Which TWO steps are required? (Choose TWO.)

Accepted Answer

Specify the Availability Zone when creating the volume.. Option D is correct because a snapshot is the source artifact from which an EBS volume is restored; without first creating a snapshot of the volume (via CreateSnapshot), there is nothing to recover from. Option C is correct because when you create a volume from a snapshot, you must specify the target Availability Zone, and the new volume must reside in the same AZ as the snapshot's source volume (snapshots are stored in S3 and are AZ-independent, but the restored volume is AZ-specific). Option A is not required because a KMS key is only needed if the snapshot/volume is encrypted, which is not stated in the scenario. Option B is not a recovery step; attaching the volume to an EC2 instance is a subsequent usage action, not part of restoring the volume from a snapshot. Option E is not required because encryption is a property set at snapshot creation time (or by copying an encrypted snapshot), not a separate step needed to recover a volume.

Answer

Configure a KMS key for the snapshot.

Answer

Attach the volume to an EC2 instance.

Answer

Enable encryption on the snapshot.