# Backend Design > Design robust backend systems and APIs. Use when users ask to plan or implement services, data models, or integrations. Use when this capability is needed. - Skill: `tomevault-io/backend-design-3` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/backend-design-3` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/backend-design-3/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/backend-design-3 --- # Backend Design Skill This skill guides the design of reliable backend systems, APIs, and data models with clear trade-offs, strong correctness guarantees, and operational readiness. ## Design Thinking - **Scope**: Identify core use cases, data flows, and integration points. - **Constraints**: Latency, throughput, availability, compliance, and deployment limits. - **Data**: Define entities, relationships, invariants, and lifecycle. - **Reliability**: Error handling, retries, idempotency, and consistency model. ## Architecture Guidelines - **API Design**: Explicit contracts, versioning, validation, and error shape. - **Storage**: Choose stores based on access patterns and durability needs. - **Performance**: Indexing, caching, batching, and async processing. - **Security**: AuthN/AuthZ, least privilege, secrets handling, auditability. - **Observability**: Logging, metrics, tracing, and alerting signals. - **Scalability**: Stateless services where possible, clear scaling boundaries. ## Output Requirements Provide a clear backend plan or implementation that includes: - Data model and key invariants - API endpoints or service interfaces - Failure modes and recovery strategy - Performance and scaling considerations - Security and observability notes ## Response Checklist ```markdown Backend Design Checklist - [ ] Confirm requirements and constraints - [ ] Define data model and invariants - [ ] Specify API contracts and error shape - [ ] Address failure modes and consistency - [ ] Cover performance, scaling, and caching - [ ] Include security and observability plans ``` --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/nicholasgriffintn) — claim your Tome and manage your conversions.