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Vercel Daemons can now call services with bindings

Vercel Daemons can now call the services in their deployment through service bindings.

Declare the binding on the daemon. It names the target service and the environment variable that receives the service's URL:

vercel.toml
[services.api]
root = "api/"
entrypoint = "main:app"


[daemons.worker]
root = "worker/"
entrypoint = "Dockerfile"
instances = { iad1 = 1 }


[[daemons.worker.bindings]]
type = "service"
service = "api"
format = "url"
env = "API_URL"

A daemon binding the api service, exposed to the worker as API_URL

The daemon calls that URL like any other HTTP endpoint. Vercel handles the internal routing, authentication, and TLS, and the service stays private:

worker/worker.ts
await fetch(new URL('jobs/next', process.env.API_URL));

Calling the bound service from the daemon with a plain fetch

Bindings point one way: services can't bind to daemons. Each instance keeps calling the deployment that started it, even after a promotion or rollback.

Learn more about daemon service bindings in the docs.