AWS Multi-Site & Hot Site DR Strategy | Deep Dive.

A deep dive into AWS Multi-Site & Hot Site Disaster Recovery (DR) Strategy.

Scope:

•         Core principles,
•         AWS-native services,
•         Traffic-routing patterns,
•        Data replication,
•        Automation,
•        Cost considerations,
•        Recovery timelines,
•        Complete high-level reference architecture.

Breakdown:

•        The concept: Multi-Site / Hot Site DR,
•        When to Use Multi-Site / Hot Site,
•        Architectural Building Blocks,
•        DR Failover Workflow (Step-by-Step),
•        Recovery Time & Recovery Point Objectives,
•        Multi-Site / Hot Site AWS Architecture Diagram Description,
•        Cost Considerations,
•        Best Practices,
•        Optional Failback Procedure.

1. The concept: Multi-Site & Hot Site DR

•        Multi-Site & Hot Site strategy is the fastest and most resilient AWS disaster recovery approach.
•        Multi-Site & Hot Site strategy keeps two (or more) environments fully active and capable of serving production traffic simultaneously.
•        Multi-Site & Hot Site strategy deployed environments  are fully active across multiple AWS Regions.

Key Properties

•         Both regions run production workloads (active-active or active-passive with warm auto-scaling)
•         Real-time data replication between Regions
•         Automatic or near-automatic failover
•         Lowest RTO (< 1–5 minutes)
•         Lowest RPO (~0 seconds) depending on datastore type
•         Highest operational cost of all DR strategies

 2. When to Use Multi-Site / Hot Site

Best for:

•         Mission-critical applications
•         Zero-downtime requirements
•         Financial, healthcare, e-commerce, or services with strict SLAs
•         Global latency reduction (via active-active)
•         Applications requiring continuous reads/writes across Regions

 3. Architectural Building Blocks

 3.1 Global Traffic Management

NB:

AWS routing services decide which Region serves the traffic (bases on Health checks).

Options:

·        Amazon Route 53

•    Latency-based routing
•    Geolocation-based routing
•    Health-check failover
•    Weighted routing for gradual migration

·        AWS Global Accelerator

•    Improves global performance
•    Intelligent edge routing
•    Much faster failover (seconds)

 3.2 Application Layer (Compute)

Common Compute Patterns

•         Active-Active
•    Both Regions serve traffic equally
•    Requires stateless or state-replicated architecture
•         Active-Passive Hot
•    Secondary Region at full capacity but not receiving traffic
•    Auto-scaled to production ready

AWS Services

•         Amazon ECS / EKS with multi-Region clusters
•         AWS Lambda with replicated versions & aliases
•         Amazon EC2 Auto Scaling across Regions
•         Amazon AppSync or API Gateway multi-region configuration

 3.3 Data Layer – Multi-Region Synchronization

Ideal solution for Databases

Service	Cross-Region Mode	RPO	Notes
Amazon DynamoDB Global Tables	Active-active	0.	Best for global workloads
Amazon Aurora Global Database	Primary + read replicas	<1s.	Fastest cross-region RPO for relational
RDS Cross-Region Read Replicas	Asynchronous	Seconds.	Good for read-heavy workloads
Amazon S3 CRR (Cross-Region Replication)	Asynchronous	Seconds.	Region-to-Region object sync

 3.4 Shared Services

•         AWS IAM (Global service)
•         AWS Secrets Manager replication setup
•         S3 for shared assets (CRR)
•         CloudFront (edge delivery)

 3.5 Automation & Infrastructure Management

•         AWS CloudFormation StackSets
•         AWS Control Tower multi-account governance
•         AWS Config multi-region compliance
•         GitOps (ArgoCD, Flux) for multi-region Kubernetes

 4. DR Failover Workflow (Step-by-Step)

If Region A fails:

1.     Route 53 / Global Accelerator detects failure

2.     Traffic is rerouted to Region B

3.     Region B’s stateless services scale automatically

4.     DynamoDB/Aurora Global DB continues operating with Region B as writer

5.     CI/CD or automation promotes Region B as the dominant region

6.     Alerts and dashboards notify administrators

7.     Optional: fail-back procedure after Region A returns

NB:

• Failover is typically automatic and completes in seconds to minutes.

 5. Recovery Time & Recovery Point Objectives

Strategy	RTO	RPO	Cost
Multi-Site / Hot Site	Seconds–Minutes	Zero–Seconds	Very High
Warm Standby	Minutes	Low	Moderate–High
Pilot Light	Hours	Low	Low–Moderate

 6. Multi-Site / Hot Site AWS Architecture Diagram Description

7. Cost Considerations

Multi-Site Hot Site is the most expensive DR strategy because:

•        Two Regions run near-full production capacity
•        Databases often require multi-region replication (premium pricing)
•        Networking between regions incurs cost
•        More operational overhead

However, this strategy delivers the best RTO/RPO in AWS.

 8. Best Practices

Compute

•         Design for stateless architecture
•         Use in-memory caches like ElastiCache Global Datastore

Data

•         Avoid multi-region writes without conflict resolution
•         Prefer services with native global replication

Network

•         Use VPC Lattice, Transit Gateway, or VPC Peering multi-region designs

Security

•         Replicate secrets across Regions
•         Use multi-region KMS keys (supported for some services)

Observability

•         Multi-region CloudWatch dashboards
•         Centralized logs in S3 with CRR

 9. Optional Failback Procedure

1.      Restore Region A
2.      Re-establish database replication with Region A as secondary
3.      Shift small percentage of traffic via weighted routing
4.      Return to active-active or primary routing controls