PRINTABLE FIELD NOTES
HTTP status codes
Use this before an interview or during a focused review.
HTTP status codes
A code describes the response semantics. It does not by itself identify which component caused the failure.
| 200 / 201 / 202 / 204 | Success / created / accepted for processing / no content. A 202 is not evidence that the background job completed. |
|---|---|
| 301 / 302 / 307 / 308 | Redirects. 307 and 308 preserve the method; inspect Location and loops. |
| 304 | Not modified in response to conditional validation; the client can reuse its stored representation. |
| 400 / 401 / 403 / 404 | Bad request / missing or invalid authentication / refused authorization or policy / not found. Check both edge and origin context. |
| 409 / 422 / 429 | Conflict / unprocessable content / too many requests. Honor relevant retry guidance and avoid unbounded loops. |
| 500 / 502 / 503 / 504 | Server error / invalid upstream response / unavailable / upstream timeout. Correlate the request and dependency timeline. |
| Cloudflare 52x | Provider-specific origin connectivity or TLS failures require the specific error documentation. A 525 handshake failure and 526 invalid origin certificate imply different tests. |