Retry Storms: How a 502 Fix Created a Thousand Duplicate Orders

A transient upstream timeout triggered a retry-heavy integration, but missing idempotency turned one request into thousands of duplicated database rows and a very busy customer service line. The fix wasn’t to slow retries down, it was to make them safe. In this post, I walk through why idempotency is the missing safety net for every HTTP-based integration, how to implement it with cheap request keys and a simple dedupe table, and the exact middleware pattern I now ship by default in ASP.NET Core.