Disaster Recovery practice questions

Enable Multi-AZ in a different Region.

Why wrong: Multi-AZ is within a single Region.

Take daily snapshots of the RDS DB instance and copy them to another Region.

Why wrong: Daily snapshots do not meet RPO of 1 hour.

Use Amazon S3 cross-Region replication for database backups.

Why wrong: S3 replication does not apply to live RDS data.

Use RDS MySQL with cross-Region read replicas in us-west-2. Use a hot standby EC2 environment with a single instance. Use Route 53 failover routing.

Why wrong: A single EC2 instance is a single point of failure; read replicas are for read scaling, not automatic failover.

Back up RDS MySQL to S3 using automated snapshots and copy them to us-west-2. Use EC2 instances with S3-mounted volumes to serve traffic from the backup.

Why wrong: Snapshot backup RPO can be up to 24 hours; restoring from S3 is slow, RTO will exceed 30 minutes.

Use RDS MySQL with Multi-AZ in us-east-1 and a second Multi-AZ deployment in us-west-2. Keep EC2 instances running in us-west-2 behind an ALB with cross-Region load balancing.

Why wrong: Multi-AZ is within a region; cross-Region load balancing is not a native feature; keeping instances running incurs cost.

Manually create and copy AMIs to the secondary region weekly

Why wrong: Manual weekly copies do not meet the 15-minute RPO.

Configure the EC2 instances in a Multi-AZ Auto Scaling group

Why wrong: Multi-AZ Auto Scaling groups replicate EC2 instances across Availability Zones within a single AWS Region, not across AWS Regions, so they cannot achieve cross-region data replication for an RPO of 15 minutes. This option is tempting because Multi-AZ deployment is a standard pattern for high availability and fault tolerance within a Region, and it would be the correct choice if the requirement were to survive an Availability Zone failure rather than a full Region outage.

Pre-warm a standby EC2 instance in the DR region.

Why wrong: EC2 warm standby alone does not address database failover.

Take hourly snapshots of RDS and copy them to the DR region.

Why wrong: Snapshot restore takes more than 15 minutes.

Use Amazon S3 Cross-Region Replication for application data.

Why wrong: S3 CRR is for object storage, not database.

Create a manual snapshot and copy it to another Region.

Why wrong: Manual process, not automated DR.

Use S3 cross-Region replication for the database.

Why wrong: S3 replication is for S3 objects, not RDS.

Enable Multi-AZ deployment.

Why wrong: Multi-AZ provides HA within a region, not DR.

Use Amazon EBS Multi-Attach to attach volumes to instances in another region.

Why wrong: Multi-Attach is for same AZ, not cross-region.

Use AWS Backup to create a backup plan with a daily backup.

Why wrong: Daily backup does not meet 15-minute RPO.

Use AWS CloudFormation to recreate the EC2 instances from a template.

Why wrong: Does not restore data.

Switch to DynamoDB On-Demand capacity mode.

Why wrong: On-Demand handles sudden spikes but is not automatic scaling based on utilization.

Implement DynamoDB Accelerator (DAX) for caching.

Why wrong: DAX reduces read load, not write throttling.

Use DynamoDB Global Tables to distribute writes.

Why wrong: Global Tables do not increase capacity in one region.

RDS Multi-AZ in the same region

Why wrong: Multi-AZ only protects within a region, not cross-region.

Amazon S3

Why wrong: S3 is not a database DR solution.

AWS Database Migration Service

Why wrong: DMS is for migration, not continuous DR.

Enable Amazon S3 cross-region replication for the EBS snapshots.

Why wrong: S3 replication does not apply to EBS snapshots; snapshots are stored in S3 but replication must be done via snapshot copy.

Use AWS Database Migration Service (DMS) to replicate data to a secondary region.

Why wrong: DMS is for databases, not for whole EC2 instances with EBS; RTO may exceed 15 minutes.

Use Amazon RDS Multi-AZ deployment in the primary Region with a standby in another Region.

Why wrong: Incorrect. Amazon RDS Multi-AZ does not support cross-Region standby; it only provides high availability within the same region. Therefore, it cannot meet the cross-Region DR requirement.

Take manual snapshots of the RDS instance every hour and copy them to another Region.

Why wrong: Incorrect. Manual snapshots taken every hour have an RPO of up to one hour, far exceeding the required 1 second RPO.

Use AWS Database Migration Service (DMS) for continuous replication to another Region.

Why wrong: AWS DMS with CDC can replicate data across Regions with low latency, but it is asynchronous and cannot guarantee a Recovery Point Objective (RPO) of 1 second. Therefore, it does not meet the strict RPO requirement.

Configure cross-Region read replicas for RDS MySQL.

Why wrong: Incorrect. Cross-Region read replicas for RDS MySQL use asynchronous replication, so the RPO is not guaranteed to be 1 second. Additionally, promoting a read replica to a primary instance is a manual process that typically takes longer than 1 minute, failing the RTO requirement.

Use automated backups with 5-minute retention.

Why wrong: Automated backups are not for failover.

Take manual snapshots every 5 minutes and copy to another region.

Why wrong: Snapshot restore takes longer than 15 minutes.

Create a cross-region read replica in us-west-2.

Why wrong: Asynchronous replication may exceed RPO.

Deploy a second ECS cluster and ALB in the secondary region with no tasks. Use cross-Region replication for ElastiCache. Use Route 53 to fail over after scaling up tasks.

Why wrong: Scaling up tasks from zero will exceed RTO.

Use a multi-region ECS service with Service Connect and Route 53 latency-based routing. Keep equal capacity in both regions.

Why wrong: Active-active is more expensive than needed for RTO 30 min.

Use pilot light by replicating ECS task definitions and copying AMIs to the secondary region. Use ElastiCache snapshot and restore. Fail over with Route 53.

Why wrong: Snapshot restore RPO is too high; pilot light not best for stateless app.

Use cross-Region Read Replicas with automatic failover.

Why wrong: Asynchronous replication may cause data loss.

Use a Multi-AZ RDS instance with a standby in another Region.

Why wrong: Multi-AZ is only within one Region.

Use AWS Database Migration Service for continuous replication.

Why wrong: DMS is not designed for low-RTO failover.

Multi-AZ deployment with synchronous replication between two instances.

Why wrong: Incorrect. Multi-AZ deployment with synchronous replication is not available for EC2 instances with EBS volumes; it is a feature of managed database services like RDS.

Single EC2 instance with EBS snapshots every 5 minutes.

Why wrong: Incorrect. EBS snapshots every 5 minutes achieve the RPO but restoring an instance from a snapshot typically takes longer than 15 minutes, failing the RTO.

Two EC2 instances in an Auto Scaling group with a warm standby.

Why wrong: Incorrect. Auto Scaling group with warm standby does not guarantee synchronous replication and may require additional time to promote the standby instance, potentially exceeding the RTO.

Single-AZ RDS instance with cross-Region snapshot copy

Why wrong: RPO is hours (snapshot interval), RTO is minutes to restore.

Multi-AZ RDS instance in us-east-1

Why wrong: Does not provide cross-Region failover.

Amazon Aurora Global Database

Why wrong: Aurora Global Database is for Aurora, not RDS MySQL.

Configure a Multi-AZ deployment for the RDS database in the primary Region.

Why wrong: Multi-AZ is for high availability within a Region, not for cross-Region DR.

Deploy the application on Amazon Aurora Global Database.

Why wrong: Aurora is a different database engine, not RDS MySQL.

Use RDS Multi-AZ in us-east-1 and failover to DR site.

Why wrong: Incorrect. RDS Multi-AZ provides high availability within a single region, not cross-region disaster recovery. It cannot meet the RPO/RTO requirements for cross-region failover.

Use AWS DMS with ongoing replication to an RDS instance in us-west-2.

Why wrong: AWS DMS with ongoing replication is primarily designed for heterogeneous database migrations or continuous data synchronisation, not for achieving ultra-low RPOs like 5 seconds with native RDS. Its change data capture (CDC) and replication process can introduce latency, making it challenging to consistently meet such a stringent RPO requirement, especially across regions. While tempting due to its "ongoing replication" capability, a native RDS cross-Region read replica or snapshot strategy is the precise mechanism for maintaining sub-minute RPOs for RDS databases.

Use Amazon Aurora Global Database.

Why wrong: Incorrect. Amazon Aurora Global Database is designed for Aurora databases, not for RDS MySQL. It is not compatible with the specified database type.

Use EBS multi-attach to attach the volume to instances in another AZ.

Why wrong: EBS multi-attach allows attaching a volume to multiple instances but only within the same AZ, so it does not help with cross-AZ recovery.

Copy the EBS volume to another AZ using the AWS Management Console.

Why wrong: You cannot copy an EBS volume directly to another AZ; the proper method is to snapshot and restore within the same region.

Take regular EBS snapshots and copy them to another region.

Why wrong: Taking snapshots and copying them to another region is for regional disaster recovery, not for AZ failures. For AZ failures, snapshots should be kept within the same region.