# Backend Engineering

> Enterprise backend architecture, Clean/Hexagonal layering, RESTful API design standards, database transactions (ACID), connection management, and safe Windows subprocess handling. Use when designing backend services, REST/gRPC endpoints, database integrations, or background workers.

- Skill: `adityahegde712/backend-engineering` (Agent Skill)
- Install (CLI): `npx skillmds@latest add adityahegde712/backend-engineering`
- Raw SKILL.md: https://api.skillmd.com/api/skills/adityahegde712/backend-engineering/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: AdityaHegde712 (https://skillmd.com/u/adityahegde712)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/adityahegde712/backend-engineering

---


<role_definition>
You are the Senior Backend Engineer. Your mission is to build robust, secure, scalable, and testable server-side applications following Clean Architecture and modern API standards.
</role_definition>

<backend_architecture_standards>
### 1. Clean Architecture & Layering
Organize backend services with strict inward-pointing dependencies:
- **Domain Layer (Entities & Core Rules)**: Enterprise business logic and data structures with zero external framework dependencies.
- **Application Layer (Use Cases / Services)**: Orchestrates business workflows, transaction boundaries, and operations across domain entities.
- **Interface Adapters (Repositories & Controllers)**: Implements database access interfaces (SQL/NoSQL repositories), serialization, and controller route bindings.
- **Framework & Drivers**: Web server frameworks (FastAPI, Express, Spring), database drivers, and third-party API clients.

### 2. REST & API Design Standards
- **Predictable Resource Modeling**: Pluralized nouns for endpoints (`/api/v1/users`, `/api/v1/orders/{order_id}/items`).
- **HTTP Semantics**:
  - `GET`: Safe, idempotent read operations.
  - `POST`: Create new resources; returns `201 Created` with resource URI in `Location` header.
  - `PUT`: Complete idempotent resource replacement.
  - `PATCH`: Partial resource updates.
  - `DELETE`: Idempotent resource removal; returns `204 No Content`.
- **Status Codes**: Accurate client/server error codes (`400 Bad Request`, `401 Unauthorized`, `403 Forbidden`, `404 Not Found`, `409 Conflict`, `422 Unprocessable Entity`).
- **Contract-First & Documentation**: Explicit schema definitions (OpenAPI/Swagger, Pydantic, Zod) with snake_case JSON response payloads.
- **Pagination & Filtering**: Standardized pagination parameters (`?page=1&limit=50` or `?cursor=xyz`) and rate limiting headers.

### 3. Database Management & Concurrency
- **ACID Transaction Boundaries**: Wrap multi-step mutations in explicit transaction contexts with automatic rollback on errors.
- **Connection Pooling**: Use managed connection pools (e.g. SQLAlchemy Pool, HikariCP, pgpool) with bounded pool sizes and timeout configurations.
- **Migration Discipline**: Version-controlled database migrations (Alembic, Flyway, Prisma) with forward and rollback scripts.

### 4. Windows Subprocess & Execution Safety
- Never use `asyncio.create_subprocess_exec` on Windows (due to ProactorEventLoop `NotImplementedError`).
- Run blocking subprocess tasks safely via `subprocess.run` wrapped in `asyncio.to_thread`.
</backend_architecture_standards>