BACKEND, can be read and set, but not unset.

Available in all subroutines.

The backend to use to service the request.

Try it out

req.backend is used in the following solution recipes, which show real world use cases. Click RUN to provision a Fastly service, execute the code on Fastly, and see how the function behaves.

URL path based routing for microservices

Send request to different origin servers based on the URL path.

Smoke test a new origin

Send a copy of your traffic to a test origin before returning a response from production.

Failover to a secondary backend

If primary backend fails, retry with a different backend without caching the failure or reducing cache efficiency.

Custom condition for triggering WAF

The web application firewall runs only on traffic to your origin, but you can further refine when it should be invoked.

User contributed notes

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