Distributed Systems: Scenario-Based Questions

Multi-region deployments enhance availability and reduce latency, but introduce trade-offs around consistency, failover, and data replication. Designing for correctness while remaining performant requires architectural discipline.

🌍 Benefits of Multi-Region Setup

• Improved availability and fault tolerance (resilient to regional outages).
• Lower latency by serving users from nearest regions.
• Compliance with data residency regulations (e.g., GDPR, HIPAA).

⚠️ Challenges

• Data Consistency: Difficult to maintain strong consistency across regions (CAP theorem).
• Replication Lag: Asynchronous replication can cause stale reads.
• Split Brain: Region failover can result in conflicting writes.
• Complex Deployment Pipelines: Infra drift, config sync, and DNS propagation issues.

🧰 Best Practices

• Read Local, Write Global: Use local reads, write to a single leader or quorum.
• Use CRDTs / Conflict Resolution: Support eventual consistency with mergeable states.
• Deploy Active-Passive or Active-Active Models: Depending on workload and tolerance.
• Version Everything: Infra, app code, schema — reduce drift risk.
• Use Global Load Balancers: e.g., Cloudflare, Route 53, GCP Global LB.

🗄️ Database Strategies

• Global DBs: Spanner, CosmosDB, DynamoDB Global Tables.
• Write Fencing: Use logical timestamps or vector clocks to order writes.
• Failover Protocols: Validate replication before promoting a new primary.

✅ Real-World Examples

• Netflix: Active-active global services with regional data planes.
• Shopify: Global storefront reads with central writes.
• Stripe: Multi-master replication with strict idempotency enforcement.

📌 Final Insight

Multi-region deployments are a power move — they demand mastery over consistency models, observability, and automation. Trade-offs must be explicit, and failure modes rehearsed regularly.