SOA-C02 Reliability and Business Continuity — Timed 100 Questions

Question 1

A company runs a web application on two EC2 instances in different Availability Zones, each with an Elastic IP address. The SysOps administrator needs to automatically route traffic to the healthy instance and fail over if one instance becomes unhealthy. The application must be accessible via a single DNS name. Which Route 53 routing policy should be used?

100 minute time limit — choose an answer to begin.

Accepted Answer

Failover routing policy. The failover routing policy in Amazon Route 53 is designed to route traffic from a primary resource to a secondary resource when the primary becomes unhealthy. In this scenario, the two EC2 instances in different Availability Zones act as primary and secondary endpoints, and Route 53 uses health checks to monitor the primary instance. If the health check fails, Route 53 automatically fails over to the secondary instance, ensuring the application remains accessible via a single DNS name.

Answer

Weighted routing policy

Answer

Geolocation routing policy

Answer

Simple routing policy

Question 2

A company runs a critical application on Amazon ECS with the EC2 launch type. The application must remain available if a single Availability Zone fails. The SysOps administrator needs to configure the ECS service for high availability. Which configuration should be used?

Accepted Answer

Use a spread placement strategy across multiple Availability Zones.. Using a spread placement strategy across multiple Availability Zones ensures that ECS tasks are distributed across distinct zones, so the application remains available if a single zone fails. With the EC2 launch type, the spread strategy can be applied at the Availability Zone level, and ECS automatically manages task placement to maintain the desired distribution. This configuration meets the high availability requirement by eliminating a single point of failure at the zone level.

Answer

Place tasks in a single Availability Zone.

Answer

Use a binpack placement strategy.

Answer

Increase the desired task count to 10.

Question 3

A company runs a stateful application on a single Amazon EC2 instance with a 200 GB EBS volume. The application data changes frequently. The SysOps administrator needs a disaster recovery (DR) plan with a Recovery Point Objective (RPO) of 1 hour and a Recovery Time Objective (RTO) of 15 minutes. The DR region is us-west-2. Which combination of steps should the administrator implement?

Accepted Answer

Take hourly EBS snapshots and copy them to us-west-2. In a disaster, launch a new instance from the snapshot and attach it.. Option A is correct: Take hourly EBS snapshots and copy them to us-west-2 using the EC2 CopySnapshot API. This meets the RPO of 1 hour. In a disaster, create a volume from the snapshot and attach it to a new instance, meeting the RTO of 15 minutes. Option B is incorrect because using both DLM and AWS Backup in that manner is not a valid architecture; AWS Backup copies recovery points it manages, not arbitrary DLM snapshots. DLM can handle cross-region copy directly, or AWS Backup can be used alone to create and copy snapshots.

Answer

Use Amazon Data Lifecycle Manager (DLM) to take snapshots every hour and use AWS Backup to copy them to us-west-2. In a disaster, restore the snapshot as a volume and attach to a new instance in us-west-2.

Answer

Enable Amazon S3 Cross-Region Replication for the EBS volume's snapshot repository.

Answer

Attach an additional EBS volume configured with RAID 1, and use rsync to replicate data every hour to a volume in us-west-2.

Question 4

A SysOps administrator needs to set up automated backups for a production Amazon RDS for PostgreSQL DB instance and copy the snapshots to another AWS Region for disaster recovery. Order the steps the administrator should take to implement this cross-region snapshot copy. (Drag each step to the correct order from first to last.) (Choose 4.)

Accepted Answer

Enable automated backups on the source DB instance.. Automated backups must be enabled on the source RDS for PostgreSQL DB instance to generate the necessary snapshots for cross-region copying. Without automated backups, there are no snapshots to copy, and the cross-region copy feature relies on these automated snapshots as the source.

Question 5

A company is designing a highly available architecture for a web application. The application uses an Application Load Balancer (ALB) and an Auto Scaling group of EC2 instances. Which TWO steps should the company take to ensure the architecture is resilient to an Availability Zone failure? (Select TWO.)

Accepted Answer

Configure the Auto Scaling group to launch instances in at least two Availability Zones.. Option C is correct because an Auto Scaling group that spans at least two Availability Zones can continue serving traffic from the surviving AZ when one AZ fails, and the ASG will also attempt to rebalance capacity across the remaining healthy AZs. Option E is correct because an internet-facing ALB with cross-zone load balancing distributes traffic evenly across all registered targets in all enabled AZs, so if one AZ becomes unavailable, the load balancer routes requests to healthy targets in the other AZs. Option A is not correct because simply raising desired capacity does not provide AZ redundancy if all instances are still placed in a single AZ or if the ASG is not configured across multiple AZs. Option B is not correct because a CloudWatch alarm on ALB 5xx errors only detects failures; it does not by itself make the architecture resilient to an AZ outage. Option D is not correct because using a single EC2 instance type does not address AZ failure resilience and may even reduce flexibility in capacity recovery.

Answer

Set the Auto Scaling group's desired capacity to a high number.

Answer

Create a CloudWatch alarm that triggers if the ALB has elevated 5xx errors.

Answer

Use a single EC2 instance type for all instances.

Question 6

A company has a production AWS account with multiple VPCs connected via a transit gateway. The security team requires that all cross-VPC traffic be inspected by a centralized network firewall appliance. The firewall is deployed in a dedicated inspection VPC. The SysOps administrator must ensure that traffic from VPC A to VPC B is routed through the inspection VPC. Which configuration achieves this?

Accepted Answer

Configure the transit gateway route tables to propagate a blackhole route for VPC A and VPC B CIDRs to the inspection VPC attachment, then have the firewall forward traffic.. Transit gateway route tables can be configured to force all inter-VPC traffic through a centralized inspection VPC. By propagating a blackhole route for the CIDRs of VPC A and VPC B to the inspection VPC attachment, the transit gateway drops traffic that is not explicitly routed through the inspection VPC. The firewall in the inspection VPC then forwards the inspected traffic back to the transit gateway, which uses separate route tables to direct the traffic to the destination VPC. This ensures that all cross-VPC traffic is inspected without requiring VPC peering or NAT gateways.

Answer

Create a VPC peering connection between VPC A and VPC B, and use route tables to send traffic through the inspection VPC.

Answer

Use security groups in the inspection VPC to filter traffic between VPC A and VPC B.

Answer

Attach a NAT gateway in the inspection VPC and configure route tables in VPC A and B to point to the NAT gateway.

Question 7

A SysOps administrator is tasked with designing a disaster recovery strategy for an Amazon RDS for PostgreSQL database. The database is currently in us-east-1. The recovery point objective (RPO) is 5 seconds, and the recovery time objective (RTO) is 1 minute. Which solution meets these requirements?

Accepted Answer

Enable Multi-AZ deployment with automatic failover.. Multi-AZ deployment for Amazon RDS provides synchronous replication to a standby instance in a different Availability Zone, with automatic failover typically completing within 1-2 minutes. This meets the RTO of 1 minute and, because replication is synchronous, the RPO is effectively zero seconds (no data loss), which satisfies the 5-second RPO requirement.

Answer

Create a cross-region read replica in us-west-2 and promote it during a disaster.

Answer

Take daily automated snapshots and copy them to another region.

Answer

Deploy the database in a single AZ and use point-in-time recovery.

Question 8

A SysOps administrator is implementing a disaster recovery strategy for an S3 bucket containing critical data. The bucket must be available within 15 minutes if the primary region fails. Data must be replicated with RPO of less than 5 minutes. Which S3 replication configuration should be used?

Accepted Answer

Enable S3 Versioning and configure S3 Event Notifications to trigger a Lambda function that copies objects to another region. The correct choice because it can meet the RPO of less than 5 minutes by using S3 Event Notifications to trigger a Lambda function that copies objects to another region in near real-time. This approach allows for sub-5-minute replication, and the bucket is available within 15 minutes after failover. S3 Versioning ensures data integrity. While CRR with RTC guarantees replication within 15 minutes, it does not guarantee sub-5-minute RPO. Options A and C either replicate within the same region or are not suitable for continuous, near-real-time replication.

Answer

Enable S3 Versioning and S3 Same-Region Replication (SRR)

Answer

Enable S3 Versioning and transfer data to another region using AWS DataSync

Answer

Enable S3 Versioning and S3 Cross-Region Replication (CRR) with replication time control (RTC)

Question 9

A company runs a critical application on EC2 instances with EBS volumes. The SysOps administrator must ensure that EBS snapshots are taken every hour and retained for 7 days. Which THREE steps should be taken to achieve this? (Choose THREE.)

Accepted Answer

Create an IAM role for DLM with permissions to create and delete snapshots. Option C is correct because Data Lifecycle Manager (DLM) requires an IAM role that grants the service permissions to create and delete EBS snapshots on your behalf; without this role the lifecycle policy cannot execute. Option D is correct because a DLM lifecycle policy is the native mechanism to define a schedule (hourly, expressed as a cron expression) and a retention rule (7 days), which automatically creates and expires snapshots. Option E is correct because DLM targets resources by tag, so the EBS volumes must carry the specific tag referenced in the policy's target specification (e.g., Backup=true) for them to be included. Option A is not needed because a CloudWatch Events rule with a Lambda function is a custom, more complex approach rather than the required DLM steps. Option B is not needed because AWS Backup, while capable of hourly backups and retention, is a separate service and not part of the DLM-based solution the question requires.

Answer

Create a CloudWatch Events rule to trigger a Lambda function that creates snapshots

Answer

Use AWS Backup to create a backup plan with hourly frequency

Question 10

A company uses Amazon Route 53 for DNS and has a domain registered with Route 53. The company wants to ensure that if the primary web server fails, traffic is automatically routed to a secondary server in a different region. The health check must consider both the server response and the application response time. Which routing policy should be used?

Accepted Answer

Failover routing policy. Failover routing policy is correct because it allows you to configure an active-passive setup where Route 53 automatically routes traffic to a secondary resource when the primary fails. By associating a health check that monitors both server response (HTTP status code) and application response time (latency threshold), Route 53 can detect failure and trigger the failover. This policy directly supports the requirement for automatic failover based on a composite health check.

Answer

Weighted routing policy

Answer

Geolocation routing policy

Answer

Latency routing policy

Question 11

Which THREE measures can be used to improve the recovery time objective (RTO) for a database running on Amazon RDS? (Choose three.)

Accepted Answer

Use a read replica and promote it during a failure.. Option A is correct because a read replica continuously receives asynchronous changes from the primary, so promoting it during a failure makes it available as a new primary much faster than restoring from a snapshot, directly reducing RTO. Option B is correct because automated backups with point-in-time recovery let you restore to any second within the retention period, which shortens recovery compared to relying only on infrequent manual snapshots. Option E is correct because Multi-AZ deployment maintains a synchronous standby in a different Availability Zone and performs automatic failover, typically in 60–120 seconds, which is the primary RDS mechanism for minimizing RTO. Option C is not correct because deletion protection only prevents accidental deletion of the DB instance; it does not affect how quickly the database can be recovered after a failure. Option D is not correct because daily manual snapshots provide a recovery point but restoring from a snapshot creates a new instance and can take much longer than failover or promotion, so it does not improve RTO as effectively.

Answer

Enable deletion protection.

Answer

Create manual snapshots daily.

Question 12

A company runs a web application on EC2 instances in an Auto Scaling group across two Availability Zones. The application uses an Application Load Balancer. The SysOps administrator receives an alert that the application is returning 503 errors. The administrator checks the CloudWatch metrics and sees that the ALB's RequestCount is normal, but the HealthyHostCount is zero. The EC2 instances are in running state and pass the EC2 status checks. What is the MOST likely cause and what should the administrator do to resolve the issue?

Accepted Answer

The ALB health check configuration is incorrect; verify the health check path and port.. Both a misconfigured ALB health check and a security group that blocks traffic from the ALB would result in HealthyHostCount=0 and 503 errors. Since the instances are running and passing status checks, either could be the cause. The administrator needs additional information, such as the health check response code or security group rules, to identify the exact issue.

Answer

The instances are out of memory; increase the instance size.

Answer

The Auto Scaling group's scaling policy is not launching new instances; update the policy.

Question 13

A company is designing a backup strategy for its Amazon S3 buckets. Which TWO methods can be used to protect against accidental deletion or overwriting of objects? (Choose two.)

Accepted Answer

Enable S3 Versioning on the bucket.. Option A (Enable S3 Versioning) is correct because versioning keeps every version of an object in the bucket, so an accidental overwrite creates a new version while the prior version remains retrievable, and an accidental delete only places a delete marker that can be removed to restore the object. Option D (Enable S3 Object Lock in compliance mode) is correct because Object Lock with compliance mode enforces a WORM (write-once-read-many) retention period during which no user, including the root account, can overwrite or delete the protected object version. Option B is not among the marked answers: MFA Delete adds an authentication requirement for permanently deleting versions or changing versioning state, but it is a supplementary control rather than a standalone protection method in this scenario. Option C is not marked because Cross-Region Replication copies objects to another bucket for durability and latency, but it does not by itself prevent deletion or overwriting in the source bucket. Option E is not marked because SSE-S3 default encryption only encrypts objects at rest and provides no protection against deletion or overwriting.

Answer

Enable MFA Delete on the bucket.

Answer

Configure S3 Cross-Region Replication.

Answer

Enable default encryption (SSE-S3) on the bucket.

Question 14

A SysOps administrator is troubleshooting an issue where an Application Load Balancer (ALB) is returning 503 errors to clients. The target group has healthy EC2 instances. Which THREE possible causes should the administrator investigate? (Choose three.)

Accepted Answer

The load balancer is not attached to a subnet.. Option A is correct because an ALB must be associated with at least two subnets in different Availability Zones; if the load balancer is not attached to a subnet (or has no valid subnet associations), it cannot route requests and returns 503 errors even if the targets are healthy. Option B is correct because the ALB's security group must allow inbound traffic on the listener port (e.g., 80/443) from clients; if the security group blocks that traffic, the load balancer cannot accept connections and clients receive 503 responses. Option C is correct because ALBs have capacity limits, and when the load balancer reaches its capacity limit (e.g., due to a surge in requests, connections, or new connections per second), it can return 503 errors to clients. Option D is not correct in this scenario because the question states the target group has healthy EC2 instances, which implies targets are registered; with no registered targets, the target group would be empty and the instances would not be reported as healthy. Option E is not correct because a misconfigured health check would typically mark targets as unhealthy, but the scenario explicitly says the target group has healthy EC2 instances, so the health check is not the cause of the 503 errors.

Answer

The target group has no registered targets.

Answer

The target group health check is misconfigured.

Question 15

A company runs a critical application on a fleet of EC2 instances in an Auto Scaling group behind an Application Load Balancer. The application is deployed in us-east-1 with instances in three Availability Zones. The company's disaster recovery plan requires failover to us-west-2 within 30 minutes with a Recovery Point Objective (RPO) of 15 minutes and a Recovery Time Objective (RTO) of 30 minutes. The application uses an RDS MySQL database and stores session data in ElastiCache Redis. The SysOps administrator has configured an RDS read replica in us-west-2 with cross-Region replication and an ElastiCache cluster in us-west-2. The administrator has also created an AMI of the EC2 instances and copied it to us-west-2. During a disaster simulation, the failover took 45 minutes because the application needed to repopulate the cache. What should the administrator do to meet the RTO? (Select TWO.)

Accepted Answer

Enable ElastiCache Global Datastore for Redis to replicate data across regions.. The 45-minute failover was due to the cold ElastiCache cluster in us-west-2 requiring application-level cache repopulation. To meet the 30-minute RTO, the cache must be warm at failover. Option A enables ElastiCache Global Datastore for Redis, which provides cross-Region replication with sub-minute RPO, keeping the us-west-2 cache synchronized in near real-time, eliminating the need for repopulation after failover. Option D (pre-warming via periodic export/import) is less reliable because it introduces a backup window, does not capture real-time changes, and may not guarantee cache freshness within the 15-minute RPO. Therefore, only Option A fully satisfies both RTO and RPO requirements.

Answer

Modify the application to store session data in the RDS database instead of ElastiCache.

Answer

Increase the size of EC2 instances in us-west-2 to handle the load faster.

Question 16

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?

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 17

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 18

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 19

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 20

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.