Anti-Patterns

1) Business Logic in Routes

Bad:

@router.post("")
def create_user(payload: UserCreate, db: Session = Depends(get_db)):
    if db.execute(...):
        raise HTTPException(409, "duplicate")

Why dangerous: - duplicates service behavior - hard to unit test - spreads business policy across transport layer

2) Cross-Module Imports

Bad:

from racerapi.modules.auth.service import AuthService

Why dangerous: - hidden coupling - extraction cost multiplies

3) Global State

Bad:

CURRENT_USER_CACHE = {}

Why dangerous: - request leakage - concurrency bugs - non-deterministic tests

4) Fake Service Layer

Bad:

def create_user(self, payload):
    return self.repo.create(payload)

Why dangerous: - layer exists without value - business rules leak upward or downward

5) Over-Engineering

Bad signs: - custom DI container - custom routing DSL - custom lifecycle engine

Why dangerous: - framework drift - onboarding friction - stale abstractions

DO

• Keep architecture explicit and boring.
• Delete abstractions that do not reduce real complexity.

DON'T

• Introduce “future-proofing” patterns with no current need.

When to Break the Rule

Never for global state and cross-module imports. Those are hard stops.