HTTP response codes

Each server response must include a correct special HTTP response status, and:

• Response codes 2 XX indicate a correctly processed request (e.g. code 200 for retrieving data, code 201 for adding a new entity, code 204 for a correct deletion etc.)
• Response codes 4 XX indicate that a request could not have been processed correctly because of some client-side data (e.g. 404 for addressing a non-existing resource).
• Response codes 5 XX indicate that an IS side error occurred during request processing (e.g. when a DB is temporarily unavailable).