Glossary: System Design Basics in C++

HTTP status codes

Also written: Status code, status codes, 200, 201, 301, 302, 400, 401, 403, 404, 409, 429, 500, 503, 301 Moved Permanently, 302 Found, 401 Unauthorized, 403 Forbidden, 404 Not Found, 409 Conflict, 429 Too Many Requests, 500 Internal Server Error, 503 Service Unavailable

The three-digit number that starts an HTTP response: 2xx means success, 4xx is the client's mistake and 5xx is the server's problem. Common codes are 200 OK, 201 Created, 301 moved for good, 302 moved for now, 400 bad request, 401 caller not identified (missing or wrong token), 403 caller known but not allowed, 404 not found, 409 conflict with current state, 429 too many requests, 500 server bug or crash, and 503 service unavailable.