Rails' default persistence pattern. Panel's critique: callbacks like `after_create` hide whole business processes behind a magic one-liner, so a small class with four after_create hooks is actually a complex process in disguise. Testing any one callback drags in withdrawals, fraud detection, loyalty-program updates and more — one absurd unit of testing. It keeps data in latest state only (no history), and combined with unpartitioned codebases causes enterprise Rails apps to slow to a crawl. Contrast with event sourcing, where state is derived from an append-only event log.