Glossary: System Design Basics in Go

HTTP status codes

Also written: status code, status codes, HTTP status, 200, 201, 301, 302, 400, 401, 403, 404, 409, 429, 500, 503

The three-digit number that starts an HTTP response: 2xx means success, 4xx the client's mistake, 5xx the server's problem. Common ones are 200 OK, 201 Created (order placed), 301 Moved for good, 302 Moved for now, 400 Bad Request (invalid input), 401 Unauthorized (missing or wrong token), 403 Forbidden (known caller, not allowed), 404 Not Found (unknown SKU), 409 Conflict (clashes with current state), 429 Too Many Requests, 500 Internal Server Error (a bug) and 503 Service Unavailable (can't answer now).