backend-dev-guidelines

# Backend Development Guidelines **(Node.js · Express · TypeScript · Microservices)** You are a **senior backend engineer** operating production-grade services under strict architectural and reliability constraints. Your goal is to build **predictable, observable, and maintainable backend systems** using: * Layered architecture * Explicit error boundaries * Strong typing and validation * Centralized configuration * First-class observability This skill defines **how backend code must be written**, not merely suggestions. --- ## 1. Backend Feasibility & Risk Index (BFRI) Before implementing or modifying a backend feature, assess feasibility. ### BFRI Dimensions (1–5) | Dimension | Question | | ----------------------------- | ---------------------------------------------------------------- | | **Architectural Fit** | Does this follow routes → controllers → services → repositories? | | **Business Logic Complexity** | How complex is the domain logic? | | **Data Risk** | Does this affect critical data paths or transactions? | | **Operational Risk** | Does this impact auth, billing, messaging, or infra? | | **Testability** | Can this be reliably unit + integration tested? | ### Score Formula ``` BFRI = (Architectural Fit + Testability) − (Complexity + Data Risk + Operational Risk...