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Difficulty: MediumDesign Traffic Routing and Failover Strategies

An organization is designing a business continuity and disaster recovery strategy for an enterprise web application deployed in the East US and West US regions.

The application must meet the following requirements:
- Route incoming HTTP requests to the closest healthy region based on latency.
- Support SSL offloading at the network edge and route traffic based on URL paths.
- Maximize availability by routing traffic away from an unhealthy region within seconds without relying on client-side DNS cache expiration.
- Provide automatic failover for the backend Azure SQL Database to the secondary region using a single connection string listener.

Which architecture solution should you recommend?

  1. A
    Deploy Azure Traffic Manager to manage global traffic routing and Azure SQL Database auto-failover groups for database replication and failover.
  2. B
    Deploy Azure Front Door to manage global traffic routing and Azure SQL Database active geo-replication (without auto-failover groups) to handle database failover.
  3. Deploy Azure Front Door to manage global traffic routing and Azure SQL Database auto-failover groups for database replication and failover.Answer
  4. D
    Deploy Azure Traffic Manager to manage global traffic routing and configure Read-Access Geo-Redundant Storage (RA-GRS) to support active-active write operations across both regions.

Answer

Deploy Azure Front Door to manage global traffic routing and Azure SQL Database auto-failover groups for database replication and failover.
The combination of Azure Front Door and Azure SQL Database auto-failover groups meets all requirements. Azure Front Door uses Anycast to route HTTP traffic based on latency, terminates SSL at the edge, performs URL path-based routing, and detects backend failures using fast health probes to redirect traffic within seconds, avoiding DNS caching delays. Azure SQL Database auto-failover groups provide a read-write listener endpoint that automatically fails over the database layer.

Step-by-Step Solution

1
Evaluate the global traffic routing requirements: SSL offloading at the edge, URL path-based routing, and immediate failover bypassing DNS caching.
Azure Front Door is selected because it is an Anycast-based Layer 7 service that supports SSL offloading, URL path-based routing, and fast failover via health probes, whereas Traffic Manager is a DNS-based Layer 4 service that cannot meet these requirements.
Traffic Manager operates at the DNS level and cannot inspect HTTP application layer features like URL paths or SSL headers, and failover is limited by DNS client-side caching.
2
Evaluate the database replication and failover requirements: automatic failover using a single connection string listener.
Azure SQL Database auto-failover groups are selected over active geo-replication.
Auto-failover groups provide a read-write listener endpoint that remains constant during a failover, and support automatic failover policies, whereas basic active geo-replication requires manual failover and connection string updates.
3
Combine the valid traffic routing and database replication strategies into a single architecture.
The final architecture uses Azure Front Door at the edge and Azure SQL Database auto-failover groups at the data layer.
This configuration meets all constraints for low failover latency, SSL offloading, path-based routing, and automated database failover.

Key Concept

Contrasting Layer 7 Anycast routing (Azure Front Door) with Layer 4 DNS-based routing (Traffic Manager) and configuring database failover mechanisms.
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Topics

Design Traffic Routing and Failover Strategies

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