Why AI-Suggested Caching Silently Corrupts Production Data

AI assistants routinely suggest a dependency injection pattern that seems correct but silently corrupts production data—caching Scoped database entities in a Singleton IMemoryCache. The bug compiles, passes tests, and runs fine locally, only causing sporadic failures under load when entities become detached from their DbContext. This pattern matters because it reveals a critical gap between how AI learns from isolated code snippets and the lifetime constraints required to prevent data corruption at scale.