Backend Design

---
name: backend-design
description: Design backend systems — REST/GraphQL/gRPC APIs, microservices, database schemas, auth, caching, message queues, scalability. Use when designing backend services, APIs, data models, distributed systems, or auth flows.
---

# Backend Design

## Workflow

Follow this systematic design process:

1. **Requirements Analysis**
   - Gather functional requirements (features, operations)
   - Define non-functional requirements (performance, scalability, availability)
   - Identify constraints (budget, timeline, technology, compliance)

2. **Architecture Selection**
   - Choose architecture pattern (monolith, microservices, serverless)
   - Select technology stack based on requirements
   - Define service boundaries and responsibilities

3. **API Design**
   - Design RESTful endpoints with proper resource modeling
   - Define request/response schemas and contracts
   - Plan versioning strategy and documentation
   - See [api-design-guide.md](references/api-design-guide.md) for REST/GraphQL/gRPC patterns

4. **Database Design**
   - Model entities and relationships
   - Design schema with normalization
   - Plan indexing and partitioning strategies
   - See [database-design.md](references/database-design.md) for relational and NoSQL patterns

5. **Security Design**
   - Design authentication flow (OAuth 2.0, JWT)
   - Plan authorization model (RBAC, ABAC)
   - Define data encryption and protection strategy

6. **Scalability & Performance**
   - Design caching strategy (Redis, CDN)
   - Plan load balancing and auto-scaling
   - Define asynchronous processing with message queues

7. **Documentation**
   - Create API specifications (OpenAPI/Swagger)
   - Document architecture decisions with Mermaid diagrams
   - Provide implementation guidelines and roadmap

## Output Structure

Present your backend design with these sections:

1. **System Overview** - High-level architecture, components, technology stack
2. **API Specification** - Endpoints, schemas, authentication, OpenAPI docs
3. **Database Design** - ERD, schema, indexes, migration plan
4. **Architecture Decisions** - Service decomposition, communication patterns, consistency model
5. **Security Implementation** - Authentication/authorization flows, encryption
6. **Scalability Plan** - Load balancing, caching, database scaling, auto-scaling
7. **Deployment Architecture** - Containers, infrastructure, CI/CD, monitoring
8. **Implementation Roadmap** - Phases, milestones, dependencies, risks

## Core Principles

- **API-first approach** - Design and document APIs before implementation
- **Security by design** - Build authentication, authorization, and encryption from the start
- **Design for scalability** - Plan for growth with caching, load balancing, and horizontal scaling
- **Plan for failure** - Include error handling, retries, circuit breakers, and graceful degradation
- **Document thoroughly** - Create clear API specs, Mermaid architecture diagrams, and implementation guides

## Reference Files

Load additional resources based on specific needs:

- **Detailed Design Process**: See [backend-design-process.md](references/backend-design-process.md) for comprehensive step-by-step workflow with examples for API design, database modeling, authentication flows, and microservices patterns

- **API Design Guide**: See [api-design-guide.md](references/api-design-guide.md) when designing RESTful APIs, GraphQL schemas, or gRPC services - includes resource modeling, status codes, versioning strategies, and documentation

- **Database Design**: See [database-design.md](references/database-design.md) for detailed guidance on relational and NoSQL database design, normalization, indexing, partitioning, and replication strategies

- **Best Practices**: See [best-practices.md](references/best-practices.md) for API design, database optimization, security hardening, performance tuning, and reliability patterns

- **Common Patterns**: See [common-patterns.md](references/common-patterns.md) for code examples of repository pattern, service layer, dependency injection, and other architectural patterns

- **Example Projects**: See [examples.md](references/examples.md) for complete architecture examples including e-commerce systems, real-time chat applications, and microservices implementations