Same question here. Also does API rewrites feature something related to the fast edge routing layer infra that vercel has?

Hi @giulianopenido, welcome to the Vercel Community!

When using rewrites to proxy requests between your Vercel projects, you will be charged for both the middleware execution and the destination function invocation, but the bandwidth costs work differently than you might expect.

Here’s the breakdown:

Bandwidth: You’ll be charged for the bandwidth from your frontend to the client, but not for the internal traffic between your Vercel projects. Vercel doesn’t charge for bandwidth between projects within their infrastructure.

Function Invocations: You’ll be charged for both:

• The middleware function that handles the rewrite
• The API function that processes the actual request

Middleware Billing: Middleware is billed per execution, not by time. Each time a request triggers your middleware (including the rewrite), it counts as one invocation. The execution time for billing purposes is only the time your middleware code actually runs, not the full request duration.

So yes, you’ll have two function invocations per API request (middleware + API function), but you won’t pay double bandwidth costs since the internal routing between Vercel projects doesn’t incur additional bandwidth charges.

Resources:

• Vercel Pricing Documentation
• Middleware Documentation
• Rewrites Documentation