Book: Event-Driven Architecture Pocket Guide Also by me: Database Playbook: Choosing the Right Store for Every System You Build My project: Hermes IDE | GitHub — an IDE for developers who ship with Claude Code and other AI coding tools Me: xgabriel.com | GitHub The card charged at 02:14 UTC. The shipping service threw a 502 at 02:14:03. By 02:14:09 your retry loop had charged the same card a second time and still produced zero shipped boxes. Customer support is now telling a person they were billed $148.50 for a product that does not exist in any warehouse system you own. That's a saga with no compensation discipline. The four steps reserve_inventory → charge_card → ship → notify look linear on a whiteboard and behave like a minefield in production: each one can fail, each one can succeed-but-time-out, and the retry that "fixes" step 3 can corrupt step 2 if step 2's compensation is not idempotent.…