Full-stack backend architecture and frontend-backend integration guide. TRIGGER when: building a full-stack app, creating REST API with frontend, scaffolding backend service, building todo app, building CRUD app, building real-time app, building chat app, Express + React, Next.js API, Node.js backend, Python backend, Go backend, designing service layers, implementing error handling, managing config/auth, setting up API clients, implementing auth flows, handling file uploads, adding real-time features (SSE/WebSocket), hardening for production. DO NOT TRIGGER when: pure frontend UI work, pure CSS/styling, database schema only.

全栈后端架构与前后端集成指南 触发条件：构建全栈应用、创建带前端的REST API、搭建后端服务、开发待办应用、CRUD应用、实时应用、聊天应用，使用Express + React、Next.js API、Node.js后端、Python后端、Go后端，设计服务层、实现错误处理、管理配置与认证、设置API客户端、实现认证流程、处理文件上传、添加实时功能（SSE/WebSocket）、生产环境优化 不触发条件：纯前端UI工作、纯CSS样式、仅数据库模式设计