Secure internal communication between services with Service Bindings
Service Bindings enable Vercel services to securely call each other within the same deployment with automatic authentication, routing, and TLS handling. Multi-service applications like a Next.js frontend calling a FastAPI backend can now communicate over Vercel's internal network without public routing, with visibility in observability dashboards.
Service Bindings make it easy for one Vercel service to securely call another within the same deployment.
When a service declares a binding for another service, Vercel automatically injects the configured environment variable. That means user code can fetch that URL normally, while Vercel handles the internal rewrite, routing, authentication, and TLS behind the scenes.
This enables multi-service applications on Vercel, like a Next.js frontend calling a FastAPI backend, while preserving service isolation and keeping routing configuration simple:
In the example above, will be able to reach the service by making a request to my_frontendmy_backendfetch()BACKEND_INTERNAL_URL.
On the FastAPI side, exposes a normal route:my_backend
That URL points inside Vercel, not at a public address. When your code fetches it, the request travels over Vercel's internal network to the same routing layer that handles every other request to your deployment, which sends it to the target service. It never hits the public route table, and Vercel sets up the TLS trust for you, so a plain HTTPS works with no certificate config.fetch
A service is only reachable if you expose it, either publicly with a rewrite route or privately with a binding.
Service-to-service calls also appear in observability, so you can see which bound service was called and how long the request took:
Service-to-service calls are billed as and . They are not billed as CDN Requests or Fast Data Transfer. See for current rates.Service RequestsFast Origin Transferservices pricing and limits
Read the to declare bindings and see the full reference.bindings documentation
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