What common mistake do developers make with Transaction behavior, why does the mistake cause problems, and what is the safer approach?

What common mistake do developers make with Transaction behavior, why does the mistake cause problems, and what is the safer approach? One recurring problem with transaction behavior is applying it without understanding the boundary it protects. Relying only on Laravel validation for uniqueness and never protecting the data with an appropriate database constraint. In addition, Tests can verify that multi-step failures leave the expected database state. Safer engineering approach: keep the responsibility in the correct layer, use the framework's supported API, validate and authorize inputs, avoid hidden side effects, and verify the behavior with tests.