senior-backend

Senior Backend Engineer

Overview

Design and implement robust, scalable backend systems with a focus on API design, service architecture, data management, and operational excellence. This skill covers RESTful and GraphQL API patterns, message-driven architecture, caching strategies, rate limiting, health checks, and full observability with OpenTelemetry.

Announce at start: "I'm using the senior-backend skill for backend system design and implementation."

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Phase 1: API Design

Goal: Define the contract before writing implementation code.

Actions

1. Define resource models and relationships
2. Design endpoint structure (REST) or schema (GraphQL)
3. Establish authentication and authorization strategy
4. Define rate limiting and throttling policies
5. Create API documentation (OpenAPI/GraphQL schema)

API Style Decision Table

Factor	REST	GraphQL	gRPC
Multiple consumers with different data needs	Poor fit	Strong fit	Poor fit
Simple CRUD operations	Strong fit	Overkill	Overkill
Real-time subscriptions	Requires WebSocket add-on	Built-in	Built-in (streaming)
Service-to-service	Good	Overkill	Strong fit
Public API	Strong fit	Good	Poor fit (tooling)
Mobile with bandwidth constraints	Overfetching risk	Strong fit	Strong fit

STOP — Do NOT proceed to Phase 2 until:

• Resource models are defined
• Endpoint structure or schema is documented
• Auth strategy is chosen
• API contract is reviewable (OpenAPI/GraphQL schema)

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Phase 2: Implementation

Goal: Build the service layer with clear separation of concerns.

Actions

1. Set up project structure with clear layering
2. Implement data access layer (repositories/DAOs)
3. Build service layer with business logic
4. Create API controllers/resolvers
5. Add middleware (auth, logging, error handling, CORS)
6. Implement caching strategy

RESTful URL Structure

GET    /api/v1/users              # List users (paginated)
GET    /api/v1/users/:id          # Get single user
POST   /api/v1/users              # Create user
PUT    /api/v1/users/:id          # Full update
PATCH  /api/v1/users/:id          # Partial update
DELETE /api/v1/users/:id          # Delete user
GET    /api/v1/users/:id/orders   # Nested resources
POST   /api/v1/users/:id/activate # State transitions