Vercel Infrastructure and Request Routing

3 posts · Jul 2020 – Sep 2025

What this trail covers

Vercel's infrastructure handles application delivery from deployment to request handling. This includes a global Edge Network with Anycast routing to Points of Presence (PoPs) for low-latency access. Vercel Firewall provides multi-layered defense at L3, L4, and L7, with a Web Application Firewall (WAF) for project-level customization. Advanced routing is managed via redirects, rewrites, and Edge Middleware, allowing for dynamic tasks like experimentation and geographic routing. The platform also...

All Vercel trails

Sep 2025How we made global routing faster with Bloom filtersThis post details the optimization of Vercel's global routing service by replacing slow JSON parsing for path lookups with Bloom filters. This change reduced memory usage by 15%, improved TTFB by 10% for the 75th percentile and above, and drastically decreased path lookup latency from hundreds of milliseconds to sub-millisecond for websites with many static paths. The implementation involved coordinating Bloom filter logic across build and routing services, using JSON Lines (JSONL) for efficient storage and transfer of Bloom filter parameters and data, and directly decoding Base64 encoded Bloom filter data in the routing service to avoid expensive string operations. This optimization also had a positive ripple effect, reducing overall routing service memory and CPU load.
Apr 2025Life of a Vercel request: Application-aware routingThis post details Vercel's application-aware routing infrastructure, explaining how framework code defines infrastructure and request handling at runtime. It introduces the concepts of route-aware and application-aware infrastructure, where the gateway has full context of deployments, domains, and logic. The post elaborates on domain aliasing, de-aliasing, and the integration of Vercel's WAF with routing metadata for application-specific firewall rules. It highlights instant global propagation for rollouts and rollbacks, achieved by updating domain aliases to point to specific deployments, resulting in millisecond-level propagation and zero downtime.
Apr 2025Update on Spain and LALIGA blocks of the internetThis post details how Spanish ISPs, under a court order from LALIGA, are blocking entire IP addresses associated with unauthorized football streaming. This indiscriminate blocking affects legitimate websites and services hosted on Vercel (and other platforms like Cloudflare and GitHub Pages) that share these IP addresses, leading to inaccessibility for users in Spain. The post highlights that this is a blanket form of censorship, ignoring SNI and not distinguishing between infringing and non-infringing services. Vercel is actively working with LALIGA to remove illegal content and is exploring mitigation strategies to restore access for affected users.
Nov 2024Life of a Vercel request: Navigating the Edge NetworkThis post details the initial stages of a Vercel request's journey through the Edge Network, focusing on Points of Presence (PoPs) and the transition to 'Edge Requests' after passing firewall and WAF evaluations. It explains how Anycast routing selects the optimal PoP and how requests are routed to Edge Regions. The post defines 'Edge Requests' as those that pass platform defenses and WAF persistent actions, highlighting their purpose and the contextual data Vercel enriches them with. It also introduces 'Fast Data Transfer (FDT)' as the mechanism for rapid data movement between users and edge regions, emphasizing its role in reducing TTFB and leveraging private fiber connections. The post provides usage metrics and optimization strategies for both Edge Requests and FDT.
Nov 2024Life of a Vercel request: What happens when a user presses enterThis post details the lifecycle of a web request on the Vercel platform, from the user pressing enter to the application logic. It elaborates on the Vercel Edge Network's role in routing requests via Anycast to the nearest PoP, the multi-layered Vercel Firewall (including L3/L4 and L7 WAF) for security, and advanced routing mechanisms like redirects, rewrites, and Edge Middleware. It highlights how framework code interacts with infrastructure at various stages, emphasizing performance and security.
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Jan 2023Behind the scenes of Vercel's infrastructure: Achieving optimal scalability and performanceThis post provides a foundational overview of Vercel's infrastructure, detailing the steps involved in deploying serverless applications and handling incoming requests. It explains the build process, including file uploads, authentication, build container execution, and resource provisioning. It also describes the request flow from DNS lookup and anycast routing to edge locations, through Kubernetes, reverse proxies, and finally to the appropriate resource (static storage, Vercel Functions, or Edge Functions).
Jan 2023Near-zero latency using Vercel Edge Functions | Customers | VercelThis post details how Read.cv leveraged Vercel's Edge Functions to deliver personalized content from a location close to their users, decreasing latency and improving Time to First Byte (TTFB). It also highlights the use of Vercel's support for wildcard domains, automatic SSL certificate generation, and DNS management for creating a multi-tenant platform, allowing users to bring their own personal domains.
Jul 2020Our new Edge and Dev infrastructureThis post introduces enhancements to the developer experience, including Fast Refresh in Next.js for near-instant UI updates and improved local development with Vercel CLI's `vercel dev` command, which offers faster startup, better stacktraces, improved memory usage, seamless environment variable synchronization, and speedier Node.js function invocations. It also details significant overhauls to Vercel's edge infrastructure, including the introduction of Vercel's own Anycast IP ranges for faster page loads (up to 6x), optimal routing, apex domain support, global redundancy, and improved interoperability. Additionally, it highlights improvements in handling large attacks and traffic spikes.