Software Design Principles

Professional software design patterns and principles for writing maintainable, well-structured code.

Critical Rules

🚨 Fail-fast over silent fallbacks. Never use fallback chains (value ?? backup ?? 'unknown'). If data should exist, validate and throw a clear error.

🚨 Strive for maximum type-safety. No any. No as. Type escape hatches defeat TypeScript's purpose. There's always a type-safe solution.

🚨 Make illegal states unrepresentable. Use discriminated unions, not optional fields. If a state combination shouldn't exist, make the type system forbid it.

🚨 Inject dependencies, don't instantiate. No new SomeService() inside methods. Pass dependencies through constructors.

🚨 Intention-revealing names only. Never use data, utils, helpers, handler, processor. Name things for what they do in the domain.

🚨 No code comments. Comments are a failure to express intent in code. If you need a comment to explain what code does, the code isn't clear enough—refactor it.

🚨 Use Zod for runtime validation. In TypeScript, use Zod schemas for parsing external data, API responses, and user input. Type inference from schemas keeps types and validation in sync.