multi-region-design

name	multi-region-design
description	Distribute globally across multiple regions for low latency, compliance, and resilience. Plan data replication, failover, and latency optimization. Use when designing global systems.

Multi-Region Design

Architect globally distributed systems with low latency, data sovereignty, and automatic failover.

Context

You are designing systems spanning multiple regions. Plan data replication, edge caching, latency optimization, and compliance. Read user distribution, latency requirements, and regulatory constraints.

Domain Context

Based on global infrastructure design (Netflix, Google, Cloudflare):

• Latency: User experiences slowness if round-trip > 100ms. Multi-region with CDN typically needed for global audience.
• Data Replication: Eventual consistency (asynchronous) for high availability. Strong consistency harder to achieve globally; usually not needed.
• Compliance: GDPR requires EU data in EU. PIPL requires China data in China. Design for data residency.
• Edge Computing: Run compute near users; offload from central region
• DNS-Based Routing: Route users to nearest healthy region using geo-DNS

Instructions

1. Map User Distribution: Where are users? 50% US-East, 30% Europe, 20% Asia? Design regions to minimize latency to majority.

2. Plan Data Replication: How quickly must data replicate to other regions? Realtime streaming (DynamoDB global tables) or batch (daily sync)? Cost increases with replication frequency.

3. Implement Read Replicas: Let each region read locally. Writes go to primary region, asynchronously replicate to replicas. Handle read-after-write consistency issues.

4. Set Up Failover: Primary region fails, automatically route to standby region. Traffic reroutes via DNS or load balancer health checks. Test failover regularly.

5. Optimize Latency: CDN caches static content near users. API Gateway in each region. Database read replicas local to region. Monitor latency by region; identify bottlenecks.

Anti-Patterns

• Multi-Region Without Plan: "Let's just replicate everything globally." Result: complexity, cost, hard to debug. Guard: Design for specific latency/compliance needs; multi-region is expensive.
• Strong Consistency Globally: Require all regions to immediately see writes. Result: latency, complexity. Guard: Accept eventual consistency; design application for it.
• No Failover Testing: Assume it works. Result: regional failure becomes outage. Guard: Monthly failover drills; practice responding to regional incidents.
• Ignoring Data Residency: Replicate data to any region for performance. Result: compliance violation. Guard: Implement geofences; restrict EU data to EU regions.

Further Reading

• The Art of Scalability by Martin Abbott and Michael Fisher — global scaling strategies
• Site Reliability Engineering by Google — multi-region deployment patterns
• High Availability Architecture — resilience and failover patterns