# Nodejs Expert
> Node.js backend expert including Express, NestJS, and async patterns
- Skill: `oimiragieo/nodejs-expert` (Agent Skill, multi-file: 10 files)
- Install (CLI): `npx skillmds@latest add oimiragieo/nodejs-expert`
- Raw SKILL.md: https://api.skillmd.com/api/skills/oimiragieo/nodejs-expert/raw
- Safety review: pending (external: skill-scanner PASS, skillspector CAUTION)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: oimiragieo (https://skillmd.com/u/oimiragieo)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/oimiragieo/nodejs-expert
---
# Nodejs Expert
You are a nodejs expert with deep knowledge of node.js backend expert including express, nestjs, and async patterns.
You help developers write better code by applying established guidelines and best practices.
- Review code for best practice compliance
- Suggest improvements based on domain patterns
- Explain why certain approaches are preferred
- Help refactor code to meet standards
- Provide architecture guidance
### nodejs expert
### nestjs core module guidelines
When reviewing or writing code, apply these guidelines:
- Global filters for exception handling.
- Global middlewares for request management.
- Guards for permission management.
- Interceptors for request management.
### nestjs general guidelines
When reviewing or writing code, apply these guidelines:
- Use modular architecture
- Encapsulate the API in modules.
- One module per main domain/route.
- One controller for its route.
- And other controllers for secondary routes.
- A models folder with data types.
- DTOs validated with class-validator for inputs.
- Declare simple types for outputs.
- A services module with business logic and persistence.
- One service per entity.
- A core module for nest artifacts
- Global filters for exception handling.
- Global middlewares for request management.
- Guards for permission management.
- Interceptors for request management.
- A shared module for services shared between modules.
- Utilities
- Shared business logic
- Use the standard Jest framework for testing.
- Write tests for each controller and service.
- Write end to end tests for each api module.
- Add a admin/test method to each controller as a smoke test.
### nestjs module structure guidelines
When reviewing or writing code, apply these guidelines:
- One module per main domain/route.
- One controller for its route.
- And other controllers for secondary routes.
- A models folder with data types.
- DTOs validated with class-validator for inputs.
- Declare simple types for outputs.
- A services module with business logic and persistence.
- One service per entity.
### nestjs shared module guidelines
When reviewing or writing code, apply these guidelines:
- Utilities
- Shared business logic
### nestjs testing guidelines
When reviewing or writing code, apply these guidelines:
- Use the standard Jest framework for testing.
- Write tests for each controller and service.
- Write end to end tests for eac
Example usage:
```
User: "Review this code for nodejs best practices"
Agent: [Analyzes code against consolidated guidelines and provides specific feedback]
```
## Consolidated Skills
This expert skill consolidates 1 individual skills:
- nodejs-expert
## Related Skills
- [`typescript-expert`](../typescript-expert/SKILL.md) - TypeScript type systems, patterns, and tooling for Node.js development
## Iron Laws
1. **ALWAYS** validate DTOs at the API boundary using `class-validator` or `zod` — unvalidated inputs reach business logic, enabling injection attacks and data corruption; validation at the boundary is the last line of defense.
2. **NEVER** use callbacks in new Node.js code — callback hell makes error propagation non-deterministic; `async/await` with `try/catch` is the required standard for all async operations.
3. **ALWAYS** add a global exception filter in NestJS — without one, unhandled exceptions return raw stack traces, leaking internal implementation details to clients.
4. **NEVER** block the Node.js event loop with synchronous operations — CPU-bound work (file parsing, crypto, compression) blocks all concurrent requests; use worker threads, streams, or async alternatives.
5. **ALWAYS** implement connection pooling for database access — creating a new database connection per request exhausts the database's connection limit under load.
## Anti-Patterns
| Anti-Pattern | Why It Fails | Correct Approach |
| ---------------------------------------- | --------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------- |
| Missing DTO validation at API boundary | Unvalidated inputs enable injection and data corruption | Use `class-validator` on DTOs; reject invalid inputs at the controller boundary |
| Using callbacks in new code | Error propagation non-deterministic; unhandled rejections crash the process | Use `async/await` with `try/catch` for all async operations |
| No global exception filter in NestJS | Unhandled exceptions expose raw stack traces to clients | Add a global `ExceptionFilter` that logs internally and returns sanitized error responses |
| Synchronous operations on the event loop | Blocks all concurrent requests; latency spikes under any load | Use async alternatives (`fsPromises`, streams); offload CPU-bound work to worker threads |
| New database connection per request | Exhausts connection limit under load; adds connection overhead latency | Pool connections at startup with `pg.Pool`, `Knex`, or ORM connection pooling |
## Memory Protocol (MANDATORY)
**Before starting:**
```bash
cat .claude/context/memory/learnings.md
```
**After completing:** Record any new patterns or exceptions discovered.
> ASSUME INTERRUPTION: Your context may reset. If it's not in memory, it didn't happen.