HTTP Status Codes & RESTful Error Handling Architecture: A Senior Engineer's Guide

Proper HTTP status code selection is fundamental to building reliable, predictable web APIs. Returning generic `200 OK` responses with `{ "error": true }` or indiscriminately throwing `500 Internal Server Error` breaks standard HTTP caching, monitoring alerts, and client retry logic.

1. Key Status Code Categories

**2xx Success:** `200 OK` (standard success), `201 Created` (resource created via POST), `204 No Content` (successful DELETE/PUT with no response body).

**3xx Redirection:** `301 Moved Permanently` (SEO permanent redirect), `304 Not Modified` (cached asset revalidation).

**4xx Client Errors:** `400 Bad Request` (malformed syntax), `401 Unauthorized` (missing or invalid auth token), `403 Forbidden` (authenticated but lacking permission), `404 Not Found` (resource does not exist), `409 Conflict` (state conflict, e.g. duplicate email), `422 Unprocessable Entity` (semantic validation failure), `429 Too Many Requests` (rate limit exceeded).

**5xx Server Errors:** `500 Internal Server Error` (unhandled exception), `502 Bad Gateway` (upstream failure), `503 Service Unavailable` (temporary overload/maintenance), `504 Gateway Timeout` (upstream timeout).

2. Standardized Error Payloads: RFC 7807

Rather than inventing ad-hoc error formats, modern APIs adopt **RFC 7807 (Problem Details for HTTP APIs)**:

json

{
  "type": "https://api.devstacktools.com/errors/invalid-parameter",
  "title": "Invalid Request Parameters",
  "status": 422,
  "detail": "The 'limit' query parameter must be an integer between 1 and 100.",
  "instance": "/api/v1/tools/search?limit=500",
  "invalid_params": [
    {
      "name": "limit",
      "reason": "Value 500 exceeds maximum allowed limit of 100"
    }
  ]
}

3. Reference and Testing Tools

Explore the complete registry of standard and non-standard HTTP status codes with our interactive [HTTP Status Code Reference](/web/http-status) and inspect request headers with our [HTTP Header Parser](/web/header-parser).

Try the Interactive Tool

1. Key Status Code Categories

2. Standardized Error Payloads: RFC 7807

3. Reference and Testing Tools