Antipattern: Fat Model / God Object

The smell

• One model owning many unrelated responsibilities (auth + billing + search + notifications + exports)
• Hundreds-to-thousands of lines, constants and scopes sprawling
• Every PR touches it; merge conflicts cluster on it

Why it hurts

• Cognitive load — readers can't tell what the model is
• Tests slow because every test loads every concern's deps
• Encourages "just add it to User" forever

The fix (in order of preference)

1. Concerns in app/models/concerns/ for behavior that genuinely belongs to the model but is logically grouped (User::Authenticatable, User::Billable)
2. Value objects / POROs for cohesive logic operating on data (PasswordStrength, SubscriptionStatus)
3. A new Active Record model when the "concern" is actually a missing entity (AccountClosure)
4. Background jobs for side effects

Avoid app/services/UserService as the dumping ground — see service-object-soup.