Sent 3 data with post request. For some reason it couldn't be saved on database table. Such as, foreign key constraint failed. then what will be the http status code?
500-599 is reserved for server errors in HTTP response status codes.
500 specifically is for Internal Server Error, which you could throw in the event that a validation error occured.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status#server_error_responses