Building Frontend Resiliency Layer by Layer
Vercel's Frontend Cloud is architected for high availability from the ground up, with resilience baked into each tier of its infrastructure rather than bolted on afterward. The goal is straightforward: keep customer applications running smoothly even when regional cloud providers experience large-scale outages or traffic surges like Black Friday.
Anycast Routing as the First Line of Defense
Every request to a Vercel-hosted site begins at a global anycast routing layer that connects each user to the nearest network edge. That edge then directs traffic to one of Vercel's primary regions.
Both layers—the routing system and the edge network—are built to keep operating even when individual components fail. If a particular network element goes offline, requests are automatically re-routed to the next closest operational region. For instance, a fiber cut that isolates the Frankfurt data center would shift traffic to Paris; if Paris were also impaired, traffic would continue onward to London, and so on across available regions.
Regional Compute with Automatic Failover
Many Vercel customers choose to run their main application logic through Vercel Functions concentrated in a single region or a small set of regions. This setup is common when a backend dependency—a database, API gateway, or headless commerce platform—is itself anchored in that same region for latency or architectural reasons.
Within any given region, Vercel Functions are by default spread across multiple availability zones (AZs), protecting against failures confined to a single AZ. But full-region outages spanning all AZs are rare but possible. For that scenario, Vercel offers Function Failover, an active-passive mode that provisions the same functions in a designated backup region. When an incident disrupts the primary region, invocations are instantly redirected to the standby, providing a robust safeguard against region-wide downtime.
For teams needing more granular control, Vercel supports configuring multiple failover regions. This flexibility matters when:
- Your application operates across several primary regions simultaneously.
- Your backend has its own specific backup region, and you want frontend compute to fail over in lockstep.
- You must comply with data residency rules—for example, keeping both primary and backup regions inside the European Union.
Fast Backend Switches with Edge Config
The third pillar of high availability is Edge Config, Vercel's low-latency global configuration store. Edge Config lets you push updates to your entire compute fleet almost instantly, with no redeployment step required. That makes it the natural tool for orchestrating backend failover on the fly.
Consider a primary database outage: instead of waiting on a slow DNS change or a fresh deployment, you can update Edge Config to point your compute at a read replica or standby database, and the new address takes effect across all regions immediately. The same mechanism works for a headless CMS or commerce provider suffering a regional outage—Edge Config lets you redirect all traffic to that vendor's backup location in seconds.
Uptime Without the Operational Burden
Building and maintaining a highly available multi-region architecture is typically a complex, expensive undertaking. Vercel packages this resilience into the platform itself, so customers get multi-AZ and multi-region redundancy, automatic failover, and global routing as defaults—no additional configuration required, and no extra infrastructure to manage.
