Optimize Node.js backend code

Apply repository/service/middleware/caching backend architecture patterns

Structuring backend code when N+1 avoidance, transaction handling, or middleware layering are needed.

• · code context (repository name, framework)
• · target architectural layer

• · pattern code examples
• · integration guidance
• · common pitfall descriptions

• · Node.js/Express/Next.js project
• · existing pattern consistency to match

• · pattern incompatible with existing project style
• · example code missing dependencies for the project

• · real code examples (TypeScript)
• · explicit N+1 fix patterns
• · transaction and caching strategies
• · tested anti-patterns called out