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Difficulty: Very hardDesign Traffic Routing and Failover Strategies

An enterprise is designing a global traffic routing and failover strategy for workloads deployed in the East US and West Europe regions. The solution must support two distinct workloads:

1. A public-facing web application that requires Secure Sockets Layer (SSL) termination at the edge, URL path-based routing (mapping `/static/*` to Azure Storage and `/api/*` to regional application gateways), Web Application Firewall (WAF) integration, and a failover recovery time objective (RTO) of less than 30 seconds.
2. A database replication synchronization daemon that communicates using a custom TCP protocol over port 5432.

Which routing and failover architecture should you recommend to meet these requirements?

  1. Deploy Azure Front Door to route and load balance the web application using its Anycast-based routing and custom HTTP probes to achieve sub-30-second failover, and deploy Azure Traffic Manager to route the database synchronization daemon traffic over port 5432 using a nested performance routing method.Answer
  2. B
    Deploy Azure Traffic Manager for both workloads, setting the DNS Time-to-Live (TTL) to 10 seconds to ensure client requests fail over to the secondary region within the sub-30-second target RTO.
  3. C
    Deploy Azure Front Door to route both workloads, adding a custom routing rule and backend pool configured for TCP port 5432 to handle the synchronization daemon traffic.
  4. D
    Deploy an Azure Cross-Region Load Balancer to route both workloads, utilizing its Layer 4 Anycast routing to achieve sub-30-second failover and mapping HTTP/HTTPS and TCP port 5432 to the regional backends.

Answer

Deploy Azure Front Door to route and load balance the web application using its Anycast-based routing and custom HTTP probes to achieve sub-30-second failover, and deploy Azure Traffic Manager to route the database synchronization daemon traffic over port 5432 using a nested performance routing method.
The correct solution uses Azure Front Door for the web application and Azure Traffic Manager for the database synchronization daemon. Azure Front Door is an Anycast-based Layer 7 load balancer that supports SSL termination, path-based routing, and WAF integration. Because it routes traffic at the edge using Split TCP, failover is detected and executed almost instantly (within seconds) via health probes, meeting the sub-30-second RTO without relying on client-side DNS updates. Azure Traffic Manager is a DNS-based routing service that can route any TCP/UDP protocol (including database traffic on port 5432) because it only resolves the DNS query to the appropriate regional endpoint IP address.

Step-by-Step Solution

1
Analyze the protocol and layer requirements of each workload.
The web application requires Layer 7 capabilities (SSL termination, URL path-based routing, WAF), while the synchronization daemon requires Layer 4 custom TCP routing (port 5432).
Identifying the required OSI layers determines which Azure load balancing services are compatible.
2
Evaluate the global failover RTO constraint for the web application.
DNS-based failover is ruled out for the web application because client-side and resolver caching will exceed the 30-second RTO. Anycast-based routing (Front Door) must be used to achieve sub-30-second failover convergence.
Anycast routes traffic directly to the nearest edge location, allowing the edge proxy to dynamically redirect requests to the alternative healthy region immediately when a probe fails.
3
Evaluate the routing capability for the custom TCP synchronization daemon.
Front Door cannot route non-HTTP/HTTPS traffic. A Layer 4 or DNS-based routing solution is required. Azure Traffic Manager is suitable because it returns the IP address of the healthy region's synchronization daemon endpoint via DNS, allowing direct custom TCP communication.
Traffic Manager operates at the DNS layer and is protocol-agnostic, whereas Front Door only supports HTTP, HTTPS, and HTTP/2.
4
Combine the services into a unified architecture.
Deploy Azure Front Door for the web application and Azure Traffic Manager for the TCP synchronization daemon.
This hybrid approach leverages the specific Layer 7 benefits of Front Door for the web application and the protocol-agnostic nature of Traffic Manager for the custom TCP workload.

Key Concept

Selecting and combining Azure global routing services based on OSI layers and failover requirements.
Estimated Time:3m 0s
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Topics

Design Traffic Routing and Failover Strategies

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