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

Consolidated Skills

This expert skill consolidates 1 individual skills:

• nodejs-expert

Related Skills

• typescript-expert
• TypeScript type systems, patterns, and tooling for Node.js development

Iron Laws

• 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.

• 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.

• ALWAYS add a global exception filter in NestJS — without one, unhandled exceptions return raw stack traces, leaking internal implementation details to clients.

• 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.

• 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:

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.