Reliability and Business Continuity — SOA-C03 Practice Quiz

Question 1

A CloudOps engineer deploys an Application Load Balancer (ALB) across three Availability Zones, but each AZ contains a different number of registered targets: AZ-a has 8 instances, AZ-b has 4, and AZ-c has 2. Users report that instances in AZ-c are experiencing significantly higher CPU utilization than instances in the other zones. What is the most likely cause of this uneven load?

Accepted Answer

Cross-zone load balancing has been disabled on the ALB, so traffic is split evenly per AZ, forcing the 2 instances in AZ-c to handle a full one-third of all requests.

Answer

The ALB distributes traffic evenly across all healthy targets regardless of AZ because cross-zone load balancing is always enabled and cannot be disabled for ALBs.

Answer

The ALB is using least-outstanding-requests routing, which always sends more traffic to zones with fewer instances.

Answer

Sticky sessions are enabled, which forces all traffic into the AZ with the fewest instances.

Question 2

A company runs a web application behind an Application Load Balancer (ALB) in a single Availability Zone. All EC2 instances in the Auto Scaling group are also in that one AZ. During a recent AZ impairment, the entire application became unreachable for several hours. The CloudOps team must redesign the architecture to survive the loss of a single Availability Zone with minimal manual intervention. Which change BEST achieves this goal?

Accepted Answer

Enable the ALB in subnets across at least two Availability Zones and configure the Auto Scaling group to launch instances into those multiple AZs.

Answer

Create a second ALB in another Region and use Route 53 failover routing to redirect traffic when the primary AZ fails.

Answer

Increase the desired capacity of the Auto Scaling group in the existing single AZ so more instances are available during an impairment.

Answer

Enable ALB access logging and configure a CloudWatch alarm to notify the team so they can manually launch instances in another AZ.

Question 3

A company runs a stateless web application behind an Application Load Balancer (ALB) with an EC2 Auto Scaling group across three Availability Zones. During scale-in events, users occasionally report failed requests and reset connections. The CloudOps engineer confirms that instances are being terminated while still actively serving in-flight requests. Which configuration change will MOST directly prevent these dropped requests during scale-in?

Accepted Answer

Increase the ALB target group deregistration delay (connection draining) so in-flight requests can complete before instances are terminated

Answer

Enable cross-zone load balancing on the Application Load Balancer

Answer

Change the target group health check protocol from HTTP to HTTPS

Answer

Increase the Auto Scaling group health check grace period

Question 4

A company runs a web application on EC2 instances in an Auto Scaling group behind an Application Load Balancer. Recently, an instance's web server process crashed, returning HTTP 503 errors to users, but the Auto Scaling group did not replace the instance for a long time. The EC2 instance itself remained running and passed all EC2 system and instance status checks. What should the CloudOps engineer configure so that Auto Scaling replaces instances that fail the application-level check?

Accepted Answer

Change the Auto Scaling group's health check type to ELB and ensure the ALB target group health check targets the application's health endpoint.

Answer

Enable EC2 detailed monitoring so that status checks are evaluated every minute instead of every five minutes.

Answer

Increase the Auto Scaling group's health check grace period so instances have more time to recover before replacement.

Answer

Attach a target-tracking scaling policy based on the ALB request count per target metric.

Question 5

A CloudOps engineer manages an EC2 Auto Scaling group that uses a launch template. The security team releases a hardened AMI monthly, and the engineer updates the launch template by creating a new version each time with the new AMI ID. However, when the Auto Scaling group scales out, newly launched instances continue to use the older AMI from the previous month. The Auto Scaling group is configured to use the launch template with version set to a specific number. What is the MOST appropriate change to ensure new instances always launch with the newest hardened AMI without manual reconfiguration each month?

Accepted Answer

Set the Auto Scaling group's launch template version to '$Latest' so it automatically uses the most recently created template version.

Answer

Enable instance refresh on the Auto Scaling group and rely on it to detect the new AMI automatically.

Answer

Set the Auto Scaling group's launch template version to '$Default' and leave the default version pointing at the original template version.

Answer

Replace the launch template with a launch configuration that references the AMI ID directly.

Question 6

A company runs a stateful application on EC2 instances behind an Application Load Balancer in an Auto Scaling group. During scale-out events, new instances require about 4 minutes to download configuration files, warm a local cache, and register with an internal service registry before they can serve traffic. Currently, the ALB begins routing requests to instances as soon as they pass the EC2 status checks, causing intermittent errors from instances that are not yet fully initialized. Which approach best ensures instances only receive traffic after initialization completes?

Accepted Answer

Add an EC2 Auto Scaling lifecycle hook for the launch (Pending:Wait) state and have the instance signal CompleteLifecycleAction once initialization finishes.

Answer

Increase the Auto Scaling group's default cooldown period to 300 seconds so new instances have time to initialize.

Answer

Change the Auto Scaling group health check type from EC2 to ELB so unhealthy instances are replaced.

Answer

Configure a target-tracking scaling policy with a longer estimated instance warmup value.

Question 7

A CloudOps engineer manages an EC2 Auto Scaling group spanning three Availability Zones behind an Application Load Balancer. After a recent AZ impairment, one AZ was temporarily removed and instances were relaunched in the two remaining AZs. Now that all three AZs are healthy again, the engineer notices the group has 8 instances in AZ-a, 8 in AZ-b, and only 2 in AZ-c, creating an uneven distribution. What is the MOST appropriate way to ensure the group automatically restores balanced capacity across all three AZs going forward?

Accepted Answer

Rely on the Auto Scaling group's built-in Availability Zone rebalancing, which launches instances in under-provisioned AZs and terminates instances in over-provisioned AZs to even out distribution.

Answer

Manually terminate three instances each in AZ-a and AZ-b so the group launches replacements evenly across all AZs.

Answer

Attach a target-tracking scaling policy on CPU utilization so scaling activity redistributes instances across the AZs.

Answer

Create a scheduled action that sets desired capacity to zero nightly and back to 18 each morning to force even redistribution.

Question 8

A CloudOps engineer manages a stateless web tier running on an EC2 Auto Scaling group backed by a single launch template that specifies one instance type and 100% On-Demand capacity. During a regional capacity event, the group failed to launch replacement instances because the specified instance type was temporarily unavailable in two of the three subnets, causing reduced availability. The team wants to improve the group's resilience to capacity shortages while also lowering cost, without managing multiple Auto Scaling groups. What should the engineer do?

Accepted Answer

Configure a mixed instances policy on the Auto Scaling group with multiple instance types and a combination of On-Demand and Spot capacity, using the capacity-optimized allocation strategy.

Answer

Create three separate Auto Scaling groups, one per subnet, each with a different instance type, and place them behind the same load balancer.

Answer

Increase the desired capacity of the existing group and enable predictive scaling so extra instances are pre-provisioned before capacity shortages occur.

Answer

Switch the launch template to use a larger instance type from the same family and enable detailed monitoring to detect launch failures faster.

Question 9

A CloudOps engineer manages an EC2 Auto Scaling group that processes long-running batch jobs. Each instance can take up to two hours to finish a job. During target-tracking scale-in events triggered by low average CPU, the ASG frequently terminates instances that are still mid-job, causing the batch work to be lost and reprocessed. The team wants scale-in to avoid terminating instances that are actively processing a job, while still allowing the group to shrink when instances become idle. What is the MOST appropriate solution?

Accepted Answer

Have the application enable instance scale-in protection on an instance when it starts a job and disable it when the job completes.

Answer

Increase the health check grace period on the Auto Scaling group so instances have more time before termination.

Answer

Switch the scaling policy from target tracking to a step scaling policy based on CPU utilization.

Answer

Set the Auto Scaling group's default cooldown period to two hours to match the maximum job duration.

Question 10

A financial services company runs a production application backed by an Amazon Aurora MySQL-compatible cluster in us-east-1. The compliance team requires a disaster recovery solution in us-west-2 with an RPO of under 1 second and an RTO of a few minutes, with minimal impact on the primary database's write performance. Which approach best meets these requirements?

Accepted Answer

Configure an Aurora global database with a secondary cluster in us-west-2 and promote it during a regional outage.

Answer

Enable AWS Backup with cross-Region copy of Aurora snapshots on an hourly schedule and restore in us-west-2 when needed.

Answer

Create a cross-Region Aurora read replica in us-west-2 using standard binlog-based asynchronous replication.

Answer

Use Aurora Multi-AZ deployment with reader instances spread across three Availability Zones in us-east-1.

Question 11

A CloudOps engineer manages an AWS Organization with 40 member accounts. Compliance requires that all EBS volumes and RDS databases across every account be backed up on a consistent schedule, with backups stored centrally and protected from deletion by individual account administrators. The team wants to enforce this centrally without deploying scripts into each account. Which approach best meets these requirements?

Accepted Answer

Use AWS Backup with a delegated administrator account, create a backup policy in AWS Organizations, and assign resources using tags across all member accounts.

Answer

Create an EventBridge scheduled rule in each member account that triggers a Lambda function to invoke EBS and RDS snapshot APIs on the defined schedule.

Answer

Deploy an AWS Backup plan in a single central account and grant that account IAM permissions to snapshot resources in all other member accounts.

Answer

Enable automated RDS backups and EBS Data Lifecycle Manager policies independently in each of the 40 member accounts.

Question 12

A financial services company runs a production Amazon RDS for PostgreSQL database in the us-east-1 Region. Compliance requires that, in the event of a full Regional outage, the company must be able to restore the database in us-west-2 with a Recovery Point Objective (RPO) of no more than 1 hour and a Recovery Time Objective (RTO) of a few hours. The CloudOps team wants a managed, centrally governed solution that requires minimal custom scripting. Which approach best meets these requirements?

Accepted Answer

Create an AWS Backup plan with a backup rule that runs hourly and configure a cross-Region copy action to copy each recovery point to us-west-2.

Answer

Enable automated RDS backups with a 7-day retention period and rely on point-in-time recovery, which automatically replicates to us-west-2.

Answer

Create a cross-Region read replica of the RDS instance in us-west-2 and promote it manually only after a Regional failure is confirmed.

Answer

Write a Lambda function triggered every 6 hours to create a manual DB snapshot and copy it to us-west-2 using the RDS API.

Question 13

A CloudOps engineer manages a production Amazon RDS for PostgreSQL database that supports an order-processing application. The business requires the ability to recover the database to any specific second within the last 5 days in case of accidental data corruption from a bad application deployment. The team currently relies only on daily automated snapshots taken at 2 AM. During a recent incident, a faulty batch job corrupted data at 3 PM, and the team could only restore to the previous night's snapshot, losing 13 hours of transactions. Which action best meets the recovery requirement going forward?

Accepted Answer

Ensure automated backups are enabled with a 5-day retention period and use point-in-time recovery (PITR) to restore to a specific timestamp.

Answer

Increase the automated snapshot frequency to run every hour using an AWS Backup scheduled plan.

Answer

Enable a Multi-AZ deployment so the standby replica can be promoted to the exact moment before corruption.

Answer

Create a cross-Region read replica and promote it to recover data from before the corruption event.

Question 14

A financial services company uses AWS Backup to protect its RDS databases, EBS volumes, and EFS file systems across multiple accounts. Auditors require documented proof that backups can actually be restored within the defined 4-hour RTO. The CloudOps team currently performs manual restores quarterly, but this is time-consuming and inconsistent. Which approach provides an automated, repeatable way to validate that backups are recoverable and meet RTO expectations?

Accepted Answer

Enable AWS Backup restore testing plans that automatically run scheduled restore jobs on selected recovery points and validate completion

Answer

Enable AWS Backup Vault Lock in compliance mode to guarantee that recovery points cannot be altered before restore

Answer

Configure cross-Region copy of all recovery points and rely on the copy job success status as proof of recoverability

Answer

Create an EventBridge rule that alerts when a backup job completes successfully and log the notification for auditors

Question 15

A financial services company must ensure that its RDS and EBS backups cannot be deleted or altered before their retention period expires, even by administrators with full IAM permissions. This is a regulatory requirement to protect against accidental deletion and ransomware. The team already centralizes backups using AWS Backup. Which action best satisfies this requirement?

Accepted Answer

Enable AWS Backup Vault Lock in compliance mode with a defined minimum and maximum retention period on the backup vault.

Answer

Attach an IAM policy to all administrators that denies the backup:DeleteRecoveryPoint action.

Answer

Enable AWS Backup Vault Lock in governance mode on the backup vault.

Answer

Enable versioning and MFA delete on the S3 bucket where AWS Backup stores recovery points.

Question 16

A company runs a batch analytics application in a single AWS Region. The workload is only used for monthly reporting and is not customer-facing. Leadership has approved a disaster recovery plan with an RTO of 24 hours and an RPO of 24 hours, and they want the lowest possible ongoing cost. The application data is stored in Amazon S3 and an Amazon RDS database. Which DR strategy best meets these requirements?

Accepted Answer

Backup and restore — replicate S3 data and copy RDS snapshots to a second Region, and provision infrastructure only when a disaster is declared

Answer

Pilot light — keep a minimal core of infrastructure (such as a stopped RDS instance) always running in the second Region

Answer

Warm standby — run a scaled-down but fully functional copy of the environment in the second Region at all times

Answer

Multi-site active/active — run full production capacity in two Regions simultaneously with Route 53 routing traffic to both

Question 17

A CloudOps engineer manages a fleet of EC2 instances backing a transaction-processing application. The business requires that no more than 1 hour of data can be lost in the event of a volume failure, and backups must be automated and retained for 30 days with the least operational overhead. The team currently uses AWS Backup with EBS snapshots. What configuration best meets the recovery point objective (RPO)?

Accepted Answer

Create an AWS Backup plan with a backup rule that runs on an hourly schedule and a 30-day retention period, assigned to the volumes via resource tags.

Answer

Create an AWS Backup plan with a daily backup rule and enable continuous backups with point-in-time recovery for the EBS volumes.

Answer

Write a Lambda function triggered every hour by EventBridge to call CreateSnapshot on each volume and a second function to delete snapshots older than 30 days.

Answer

Create an AWS Backup plan with a daily backup rule and copy each recovery point to a second Region every hour to reduce the RPO to 1 hour.

Question 18

A media company runs a video transcoding fleet on an EC2 Auto Scaling group behind an Application Load Balancer. During major live events, incoming jobs can spike from 20% to 90% CPU utilization within a couple of minutes, and the current target-tracking policy scales too gradually, causing a growing job backlog. The CloudOps engineer needs a scaling approach that adds capacity in proportion to how severe the breach is—launching more instances for larger spikes and fewer for minor ones. Which scaling configuration best meets this requirement?

Accepted Answer

Replace the target-tracking policy with a step scaling policy that defines multiple step adjustments based on the magnitude of the CloudWatch alarm breach.

Answer

Keep the target-tracking policy but lower the target CPU value to 40% so scaling starts earlier.

Answer

Configure a scheduled scaling action that increases desired capacity at fixed times each day.

Answer

Enable a simple scaling policy that adds a fixed number of instances whenever CPU exceeds 70%, with a 300-second cooldown.

Question 19

A CloudOps engineer manages a stateless web application running on an EC2 Auto Scaling group behind an Application Load Balancer. Traffic is unpredictable and fluctuates throughout the day. The team wants the group to automatically maintain average CPU utilization at approximately 50% across all instances, adding or removing capacity smoothly as load changes, with minimal manual tuning of thresholds. Which scaling configuration best meets this requirement?

Accepted Answer

Configure a target-tracking scaling policy using the ASGAverageCPUUtilization metric with a target value of 50%.

Answer

Configure two step scaling policies triggered by CloudWatch alarms at 40% and 70% CPU to add and remove instances.

Answer

Configure a scheduled scaling action that increases capacity during business hours and decreases it overnight.

Answer

Configure a simple scaling policy with a 300-second cooldown that adds one instance when CPU exceeds 50%.

Question 20

A company runs a stateful web application behind an Application Load Balancer with an EC2 Auto Scaling group. Users report that during scale-in events (when the ASG terminates instances), some active sessions receive HTTP 5xx errors and in-flight requests are abruptly cut off. The operations team wants to ensure instances finish serving existing requests before termination completes, without keeping instances registered indefinitely. Which action BEST addresses this?

Accepted Answer

Configure the target group's deregistration delay (connection draining) to allow in-flight requests to complete before the instance is deregistered

Answer

Increase the ALB health check interval so instances are marked healthy longer during termination

Answer

Enable cross-zone load balancing on the ALB to evenly distribute connections during scale-in

Answer

Switch the ASG termination policy to OldestInstance so long-running sessions are preserved

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