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Aishwary Gathe
Aishwary Gathe

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Building Two-Region Failover Routing on AWS — My Hands-On Learning

Did You Ever Imagine How Businesses Stay Online Even When a Whole Region Fails?

We often take the internet for granted. A website just “works.” But behind the scenes, massive infrastructure decisions ensure that even if an entire cloud region fails, services continue without interruption.

This week, I explored Two-Region Failover Routing on AWS, a hands-on exercise that gave me a practical understanding of high availability (HA) and disaster recovery (DR).


🔹 Why Multi-Region Architecture?

Cloud providers like AWS offer highly available infrastructure within a region. But what happens if the entire region goes down? Power failures, natural disasters, or large-scale outages could make even the most redundant single-region architecture unavailable.

That’s where multi-region failover routing comes in. By replicating infrastructure across two AWS regions, traffic can seamlessly shift if one region experiences downtime.


My Two-Region Setup

I built identical environments in Region 1 and Region 2. Here’s the breakdown of resources:

Region 1 (Primary)

  • 1 VPC with 4 subnets (2 public, 2 private)
  • 1 Internet Gateway
  • 2 Route Tables (public + private separation)
  • 2 Security Groups (public-facing & internal communication)
  • 4 EC2 instances spread across subnets
  • 1 Target Group for application-level routing
  • 1 Load Balancer (ALB for distributing requests)
  • 1 AMI Image (to replicate app servers consistently)
  • 1 Launch Template (to standardize instance creation)
  • 1 Auto Scaling Group (ASG) for elasticity

Region 2 (Secondary / Failover)

A mirror setup to Region 1, ensuring identical infrastructure:

  • 1 VPC, 4 Subnets, 1 Internet Gateway
  • 2 Route Tables, 2 Security Groups
  • 4 EC2 Instances
  • 1 Target Group + 1 Load Balancer
  • 1 AMI Image + 1 Launch Template
  • 1 Auto Scaling Group

By using the AMI image and launch templates, I ensured both regions had consistent server configurations.


The Key – Failover Routing

After creating infrastructure in both regions, I configured AWS Route 53 Failover Routing.

  • Primary Region: Handles all traffic by default.
  • Secondary Region: Remains on standby. It only starts receiving traffic if health checks detect that the primary region is unhealthy or unavailable.

This means users never notice downtime — the DNS automatically reroutes them to the secondary region.


What I Learned

  1. Infrastructure Parity Matters – Keeping regions consistent avoids unpredictable behavior during failover.
  2. Health Checks Drive Automation – Without them, Route 53 cannot know when to shift traffic.
  3. Scalability with Auto Scaling Groups – Ensures that whether in normal conditions or failover, workloads scale based on demand.
  4. Real-World Relevance – This is how global-scale companies like Netflix, Amazon, and fintech providers maintain near 100% uptime.

Final Thought

Did you ever imagine that keeping a website online might mean running entire clones of your infrastructure across continents? That’s the power of cloud computing.

This exercise made me appreciate how resilient architectures are built — not just with code, but with thoughtful planning of networks, routing, and automation.


👉 What do you think? Should I create a step-by-step guide on actually setting this up for beginners?

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