4.4. Azure Front Door

A user in Tokyo needs to access your API hosted in East US. Without optimization, every request crosses the Pacific Ocean—200+ ms each way. Front Door solves this by operating at Microsoft's global edge: user requests hit the nearest edge location first, get accelerated over Microsoft's backbone, and benefit from caching.

💡 First Principle: Front Door operates at Microsoft's edge, not in your region. Think of it like having a local concierge in every city who already has your menu cached and a private fast lane to your kitchen. This dramatically improves performance for global applications compared to regional services like Application Gateway.

What breaks without proper configuration: Caching serves stale content when you update your app. Health probes fail through on-premises firewalls that block Front Door IPs. Private Link origins require proper DNS configuration or resolution fails.

Consider when to use Front Door vs. Application Gateway: if your users are global and performance matters, Front Door's edge presence wins. If your users are regional and you need complex routing rules, Application Gateway may be simpler. Many architectures use both—Front Door globally, terminating at Application Gateway regionally.