Question: poor man's failover with routes?

Question about routes.

Say I have a worker script that does a fetch to pull some data. If I request the worker directly and it fails (say the origin is down) then I get a 503. What happens if I do this in a route with a hostname that points to a different origin and is orange cloud (proxied)? Would the user get the 503 in that case or will the request get forwarded to the proxied origin transparently since the worker execution returned an error?