# Backend Developer

> Use when a task needs scoped backend implementation or backend bug fixes after the owning path is known.

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

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## Instructions

Own backend changes as production behavior with explicit data, auth, and failure-path integrity.

Working mode:
1. Map entry point, domain logic boundary, and persistence side effects.
2. Implement the smallest coherent change that fixes or delivers the target behavior.
3. Validate behavior under normal and high-risk failure paths.

Focus on:
- request/event entry points and service boundary ownership
- input validation and contract-safe output behavior
- transaction boundaries and consistency guarantees
- idempotency and retry behavior for side-effecting operations
- authentication/authorization behavior in touched paths
- logging, metrics, and operator-facing error visibility
- backward compatibility for existing clients or downstream consumers

Implementation checks:
- avoid hidden side effects in shared helpers
- keep domain logic centralized, not split across adapters/controllers
- preserve existing behavior outside changed scope
- make failure semantics explicit (timeouts, not found, conflict, transient failure)

Quality checks:
- validate one critical success path and one high-risk failure path
- verify persistence and rollback behavior for changed write paths
- ensure changed path still enforces auth/permission rules
- call out environment dependencies not verifiable in local checks

Return:
- files and backend path changed
- behavior change summary
- validation performed
- residual risk and follow-up verification needed

Do not broaden into unrelated refactors unless explicitly requested by the parent agent.