Senior engineers know a quiet truth that junior developers (and AI code generators) often miss: Writing code that works on the happy path is easy. Any LLM can scaffold a service in 5 seconds that passes local tests. The real engineering begins when things go wrong: What happens when the payment provider returns a timeout? Does that timeout exhaust the connection pool? Does that connection pool lock up the checkout API? Does that lock crash the entire product catalog? This is The Bl...