HTTP status codes / 5xx — Server errors
Temporarily down: overload, maintenance or no healthy backends.
The server cannot handle the request right now — maintenance windows, overload shedding, or a load balancer with zero healthy targets. Retry-After may say when to come back.
curl -i https://httpbin.org/status/503
Same request, no terminal: paste this into the cURL converter for native code, or straight into ReqPad on your phone.
Honor Retry-After, add backoff, and check the provider status page; for your own infra, look at health checks and autoscaling events.
Server-side note: Honor Retry-After. For your own infra: inspect health-check failures and scaling events around the timestamp.
The fastest way to pin down a 503 is to reproduce the exact request and inspect what actually went over the wire — status, headers, timing and body, without your app code in the way. That is what an API client is for; ReqPad does it from your phone, with every request saved to history.
500 Internal Server Error · 501 Not Implemented · 502 Bad Gateway · 504 Gateway Timeout · 505 HTTP Version Not Supported · 506 Variant Also Negotiates — or the full reference.
Build the request, send it, read status + headers + timing — on your iPhone. Free to start.