# Multi-Region Resilience: Failover, Data, and DNS

URL: https://www.devopsness.com/blog/multi-region-resilience-failover-data-and-dns
Author: Kiril Urbonas
Published: 2025-11-02
Updated: 2025-11-02
Categories: Cloud
Tags: AWS, Terraform, Monitoring

Summary: Design for region failure. Active/passive and active/active, data replication, and failover testing.

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# Multi-Region Resilience: Failover, Data, and DNS

Single-region risk is high. Multi-region design improves availability and disaster recovery.

## Patterns

- **Active/passive**: One primary region; failover to secondary on failure. RTO/RPO depend on replication and DNS.
- **Active/active**: Traffic in multiple regions; better latency and availability, harder data consistency.

## Data

- **Replication**: Async for RPO tolerance; sync for strong consistency (with latency tradeoff).
- **Conflict resolution**: Last-write-wins or application-defined; test conflict scenarios.

## DNS and Traffic

- **Route53 / global load balancers**: Health checks and failover or weighted routing.
- **TTL**: Lower TTL before failover to reduce propagation delay; balance with DNS load.

## Best Practices

- **Run failover drills** regularly; automate where possible.
- **Document** RTO/RPO and runbooks; align with business.
- **Monitor** replication lag and health in both regions.

Multi-region adds cost and complexity; start with critical paths and expand.