# ADR-009: Persistence Independence

## Status
Accepted

## Context
We need to ensure that business logic is not coupled to persistence implementation.

## Decision
Same use cases must produce same results regardless of repository implementation.

### Verification Method
1. Run test with InMemoryRepository
2. Run test with PostgresRepository (when implemented)
3. Compare results
4. If different, adapter is wrong

### Architecture Rules
- Domain: 0 external dependencies
- Application: only domain + contracts
- Infrastructure: may depend on external libraries, never reverse
- Persistence Independence: same use cases, same results

## Consequences

### Positive
- Strong architecture verification
- Easy to swap implementations
- Tests document expected behavior

### Negative
- Need to maintain two test suites
- PostgreSQL tests require database setup

## Related
- ADR-006: In-Memory Adapters for Testing
- ADR-008: PostgreSQL Adapters for Production