Status Codes

Beyond the broad category from the HTTP course (2xx/3xx/4xx/5xx), REST APIs use SPECIFIC codes within each category to communicate precisely what happened — picking the right one is part of designing a good API, not just an afterthought.

def status_category(code):
    if 100 <= code < 200: return "informational"
    if 200 <= code < 300: return "success"
    if 300 <= code < 400: return "redirection"
    if 400 <= code < 500: return "client_error"
    if 500 <= code < 600: return "server_error"
    return "unknown"

Choosing the right code for each operation makes an API predictable and self-documenting — a client can react correctly to a status code alone, without parsing the response body:

def choose_status_for_operation(operation, success):
    mapping = {
        ("create", True): 201, ("create", False): 400,
        ("delete", True): 204, ("delete", False): 404,
        ("read", True): 200, ("read", False): 404,
    }
    return mapping.get((operation, success), 500)

A common mistake: returning 200 OK for EVERYTHING, with the real success/failure info buried in the response body. That forces every client to parse the body just to know if something worked — status codes exist precisely so that layer of information doesn't require parsing anything.