vercel-services

Define both as entries under the services key in vercel.json, each with its own root directory. Then add ordered top-level rewrites, such as sending /api/(.*) to the backend service and a catch-all to the frontend.

Declare a binding on the caller service naming the target service and an environment variable, such as BACKEND_INTERNAL_URL. Vercel injects a deployment-aware URL at runtime, letting services communicate privately without public routes.

Vercel preserves the original request path, so /api/users reaches the backend as /api/users. Either configure the backend to handle the prefix, such as FastAPI root_path, or strip it with a service-scoped rewrite.

Yes. A service without a matching top-level rewrite is unreachable from the public internet and only accessible through bindings. Note that bindings grant network reachability, not application-level authentication.

Preview deployments get a single generated URL, so host-based rewrite rules never match there. Keep a subpath rewrite to the same service and use a relative URL like /api in the frontend.

Use separate projects when teams need to deploy and roll back services independently, since every Services deployment ships all services together. Also skip Services when one framework like Next.js can own the whole app.