> For AI agents: the complete documentation index is available at https://nhanbe.id.vn/llms.txt, the full documentation bundle is available at https://nhanbe.id.vn/llms-full.txt.

# Anti-Patterns and Misuse

Patterns are tools, not goals. These are common misuses that reduce clarity and maintainability.

## Common anti-patterns

### Overusing Singleton

Singletons introduce global state and hidden dependencies. Prefer dependency injection or a scoped service.

### Factory for everything

Factories add indirection and boilerplate. Use them only when creation logic varies or needs isolation.

### God Facade

A facade that grows into a mega-service becomes a bottleneck and breaks modularity. Split by responsibility.

### Inheritance for minor changes

If you change only small behavior, prefer composition (Strategy/Decorator) over subclassing.

### Using patterns without a problem

If the code is simple, keep it simple. Patterns should solve real constraints.

## Red flags

- You can’t explain why a pattern is used.
- The pattern adds more code than it saves.
- Testing became harder after adding the pattern.