Every API response includes a status code. Most early stage engineers only know 200, 404, and 500.
Here are the ones that can set you apart:
2xx - Success
200 OK → Request succeeded
201 Created → New resource created (POST)
204 No Content → Success, nothing to return (DELETE)
3xx - Redirection
301 Moved Permanently → URL changed forever
302 Found → Temporary redirect
4xx - Client Error
400 Bad Request → Malformed request
401 Unauthorized → Not authenticated
403 Forbidden → Authenticated, but not allowed
404 Not Found → Resource doesn’t exist
5xx - Server Error
500 Internal Server Error → Something broke
502 Bad Gateway → Upstream server failed
503 Service Unavailable → Server overloaded
504 Gateway Timeout → Upstream didn’t respond
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