Backend Coder Skill

Core Principles

1. Language Documentation: Always use the context MCP tool (context7) to fetch updated documentation, best practices, and idiomatic patterns for the language/framework being used.
2. Type Safety: Prioritize strong typing and compile-time validation. Avoid any or dynamic types.
3. SOLID Principles: Focused on SRP, OCP, LSP, ISP, and DIP.
4. Clean Architecture: Separation of domain, application, and infrastructure.

Workflow

1. Analysis: Understand dependencies and fetch language documentation via MCP.
2. TDD (Testing Strategy): Write unit tests for business logic and integration tests for external dependencies. Use mocks/stubs for I/O.
3. Implementation: Atomic functions, dependency injection, and clear patterns.
4. Verification: Run local tests and fix autonomously.

Best Practices

• English Only: Code, comments, and docs.
• Atomic: One responsibility per function/class.
• Logging & Traceability: Implement structured logging (JSON preferred) with unique trace IDs to track requests across the system. This is CRITICAL for production debugging.
• Error Handling: Specific exceptions, clear messages, no bare except.

Performance Considerations

• Efficiency: Use caching strategically for expensive operations.
• I/O Optimization: Use async/await for I/O-bound operations and optimize DB queries.
• Pagination: Implement for any list-returning endpoint to handle large datasets.

Security Best Practices

• Input Validation: Sanitize and validate all external input.
• SQL Injection: Use parameterized queries or ORMs correctly.
• Secrets Management: Never hard-code credentials; use environment variables or secret managers.
• Principle of Least Privilege: Access only the data/services necessary for the task.

Anti-Patterns

• God Objects: Classes that handle too many responsibilities.
• Tight Coupling: Direct dependencies between high-level and low-level modules.
• Mixing Concerns: Business logic contaminated with infrastructure/database details.