How the vercel edge network works

Vercel is a platform for deploying modern web applications, and it uses a sophisticated edge network to optimize the delivery of content and improve performance. Here's a detailed look at how Vercel handles requests and leverages its edge network:

Vercel's Architecture and Edge Network

1. Edge Network:

   • Vercel deploys a global edge network consisting of numerous Points of Presence (PoPs) strategically located around the world.
   • These edge servers handle static content delivery and certain dynamic requests, reducing latency by serving users from the closest location.

2. Main Server (Backend):

   • The main server or backend (often running on serverless functions) handles dynamic content generation, API requests, and server-side logic that cannot be executed on the edge.

Request Handling on Vercel

1. Static Content:

   • Deployment: When you deploy a site to Vercel, static assets like HTML, CSS, JavaScript, images, and other files are distributed across Vercel’s edge network.
   • Request Handling: When a user requests a static file, the request is routed to the nearest edge server, which serves the content directly from the cache. This minimizes latency and speeds up content delivery.

2. Dynamic Content:

   • Edge Functions: Vercel supports serverless functions (referred to as "Edge Functions" or "Serverless Functions"), which can run on the edge network.
     • These functions handle lightweight dynamic content generation and API requests directly at the edge.
     • They are ideal for scenarios requiring low latency, such as personalization, authentication, or A/B testing.
   • Main Serverless Functions: For more complex dynamic requests, server-side rendering (SSR), or backend processing that can't be efficiently handled at the edge, Vercel routes the requests to serverless functions running in centralized data centers.
     • These functions are scalable and can be triggered on-demand, handling tasks that require more processing power or access to backend databases.

3. Routing and Caching:

   • Routing: Vercel’s intelligent routing system determines whether a request should be served by an edge server or routed to a serverless function based on the type of content requested.
   • Caching: Edge caching is used extensively to store and serve frequently accessed static content. Vercel also supports caching of dynamic content generated by serverless functions, where appropriate, to further enhance performance.

How Decisions Are Made

• Static vs. Dynamic Content: Vercel automatically differentiates between static and dynamic content based on the deployment configuration and file types. Static files are deployed to the edge, while dynamic content is routed through serverless functions.
• Edge vs. Main Server:
  • Edge Server: If a request can be fulfilled by cached static content or handled by an edge function with minimal processing, it is served directly from the nearest edge server.
  • Main Server: If a request requires complex processing, database interactions, or generates dynamic content that can't be cached, it is routed to a serverless function in a data center.
• Geographic Proximity: Requests are routed to the nearest edge server to reduce latency. Vercel’s network uses DNS-based routing and other mechanisms to ensure users are connected to the optimal PoP.

Example Workflow

1. User Requests a Static Page:

   • The request is routed to the nearest edge server.
   • The edge server serves the static HTML, CSS, and JS files directly from its cache.

2. User Requests Dynamic Content:

   • The request is routed to an edge function if it involves lightweight processing.
   • If the processing requires more resources or backend access, the request is forwarded to a serverless function running in a central data center.
   • The result is then returned to the edge server and served to the user.

3. API Request:

   • An API request that can be handled by an edge function (e.g., simple data retrieval or transformation) is processed at the edge.
   • More complex API requests involving database queries or extensive processing are sent to the main serverless functions.