CrateDB HTTP SQL Endpoint
CrateDB's native developer interface: a JSON-over-HTTP SQL endpoint. Clients POST a JSON body ({"stmt": "...", "args": [...], "bulk_args": [[...]]}) to /_sql (default port 4200) and receive cols/rows/rowcount/col_types. PostgreSQL wire protocol is also supported. Errors return a structured {"error": {"code": N, "message": "..."}} envelope with codes in the 4000-5035 range.