mern-stack

Design and implement a RESTful Express API: route structure, validation, error handling, pagination, and OpenAPI documentation

Implement complete JWT authentication for a MERN app: register, login, refresh, logout, protected routes in Express and React

Build a React component or page: structure, state management, data fetching with React Query, form handling, accessibility, and tests

Build a full MERN feature end-to-end: schema → API → service → React component with state management

Review MERN code for security, performance, architecture, and best practices

Design a MongoDB schema with Mongoose: embed vs reference, indexes, validation, and migration plan

Express.js REST API: router organization, controller pattern, async error handling, request validation with Joi/Zod, consistent response formats. Use when building Express API endpoints.

Express middleware patterns: error handling middleware, request validation, rate limiting, logging, auth middleware, custom middleware composition. Use when building or debugging Express middleware chains.

Complete JWT auth flow: registration, login, access + refresh token pair, httpOnly cookies, token rotation on refresh, logout (server-side invalidation), silent refresh. Use when implementing auth in a MERN app.

MERN project structure, layered architecture (routes -> controllers -> services -> repositories), folder conventions, env setup, monorepo vs separated repos. Use when starting a new MERN project or restructuring an existing one.

Deploying MERN apps: Dockerfile for Node.js/React, docker-compose for local dev, CI/CD with GitHub Actions, MongoDB Atlas, environment configuration, health checks, and zero-downtime deployment. Use when containerizing or deploying a MERN app.

MERN stack security: NoSQL injection prevention, XSS, CSRF, secure headers, input sanitization, dependency auditing, secrets management. Use when securing or auditing a MERN application.

Testing MERN stack apps: unit testing Express services with Jest, integration testing APIs with Supertest, React component testing with Testing Library, and MongoDB test setup. Use when writing or improving tests for a MERN app.

Schema design with Mongoose: embedded vs referenced documents, validation rules, compound indexes, TTL indexes, sparse indexes. Use when designing MongoDB schemas for a Node.js application.

Node.js patterns for production: async/await error handling, streams, worker threads, clustering, event emitter patterns, graceful shutdown. Use when building or optimizing Node.js backend services.

React component patterns: composition, compound components, render props, controlled vs uncontrolled, accessibility, error boundaries, and performance optimization. Use when designing or refactoring React components.

Hook patterns: useEffect dependency array correctness, useMemo/useCallback tradeoffs, custom hook extraction, avoiding stale closures, common pitfalls. Use when writing or debugging React hooks.

React state management: useState, useReducer, Context API, Zustand, React Query for server state. Covers when to use each, anti-patterns, and optimistic updates. Use when designing state architecture for React apps.