504 vs 503: What Actually Triggers Each in nginx, ALB, and Cloudflare

You're staring at a 5xx in your logs at 2am. Is it a 503 or a 504, and does the difference actually change what you do next? Yes — a lot. 503 means something upstream is deliberately refusing the request right now. 504 means something upstream accepted the request and then never answered in time. That's an availability problem versus a latency... Weiterlesen