Sometimes, the most useful improvements to a project come from someone asking a question you had not fully considered. While working on ShopEase, my Spring Boot e-commerce backend, I implemented idempotency protection to prevent duplicate checkout requests. My initial approach returned HTTP 409 Conflict whenever an Idempotency-Key was reused. Then Andrei Ovcharenko commented on my Dev.to article with an important observation: What if the order commits successfully, but the client nev...