Build production-ready Node.js backend services with Express/Fastify, implementing middleware patterns, error handling, authentication, database integration, and API design best practices.
SkillScore86Maintained
Automatic
◆Coding pack
Last verified 8/21/2026
What it changes
Passed 19 of 22 test cases with the skill, and 17 of 22 without it.
Without skill77%
With skill86%
Checks it passed that the model alone missed
Checks whether req.user.roles contains any specified authorized role.
Checks if error is an instance of AppError before extracting status codes.
Passes validation and authentication errors to Express error handling via next().
3 fixed16 passed either way2 still failing1 broke
Pass-rate lift
+9 pp
Tokens
+251%
Agent turns
0%
Response time
-4%
Model gemini-3.6-flashMeasured 8/21/2026v119 of 22 cases passed with skill
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 3 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 3
Prompt
Can you provide production-grade Express middleware snippets written in TypeScript for handling API request validation and JWT-based authentication? Please include one middleware that checks authorization headers for access tokens and attaches the decoded payload to the request, and another middleware that uses Zod to validate incoming body/query/params data before passing control to the controller.
What was checked, without and with the skill
Checked
Without skill
With skill
Passes validation and authentication errors to Express error handling via next().
Missed
Passed
Validates req.body, req.query, and req.params together in a single schema pass.
Passed
Passed
case-01 · gemini-3.6-flash · 8/21/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md1015 linessingle file
Node.js Backend Patterns
Comprehensive guidance for building scalable, maintainable, and production-ready Node.js backend applications with modern frameworks, architectural patterns, and best practices.
When to Use This Skill
Building REST APIs or GraphQL servers
Creating microservices with Node.js
Implementing authentication and authorization
Designing scalable backend architectures
Setting up middleware and error handling
Integrating databases (SQL and NoSQL)
Building real-time applications with WebSockets
Implementing background job processing
Core Frameworks
Express.js - Minimalist Framework
Basic Setup:
import express, { Request, Response, NextFunction } from 'express';
import helmet from 'helmet';
import cors from 'cors';
import compression from 'compression';
const app = express();
// Security middleware
app.use(helmet());
app.use(cors({ origin: process.env.ALLOWED_ORIGINS?.split(',') }));
app.use(compression());
// Body parsing
app.use(express.json({ limit: '10mb' }));
app.use(express.urlencoded({ extended: true, limit: '10mb' }));
// Request logging
app.use((req: Request, res: Response, next: NextFunction) => {
console.log(`${req.method} ${req.path}`);