Mock JSON endpoint returning HTTP 504

Live demo endpoint

Any method, any path. Returns 504 Gateway Timeout with Content-Type: application/json. OPTIONS returns 204 with CORS headers.

Call it with curl

curl -i https://demo-json-504.supercrontab.com/

Call it with fetch

const res = await fetch("https://demo-json-504.supercrontab.com/");
console.log(res.status); // 504
const body = await res.json();

What HTTP 504 Gateway Timeout means

When you see it

A proxy waited for the upstream app and gave up. The request may or may not have been processed.

What a client should do

Retry only idempotent requests, with backoff. For POSTs use an idempotency key so a retry cannot double-apply.

Retry?

Yes, with backoff

Sample response body

{"ok":true,"id":42,"items":["alpha","beta","gamma"]}

The default for REST APIs. Parse it with response.json() and check the ok field.

Questions