Every page gets one

The mistake

A synthetic-monitoring script checks uptime by calling the real checkout API and completing a real purchase every minute, instead of hitting a dry-run or staging endpoint. There's no idempotency guard, no order cap, and no circuit breaker tied to alerting, so the check keeps executing real transactions on a live payment method even after the on-call engineer stops watching it. The site's own 'someone just bought X' notification, meant as a marketing signal, ends up as the only feedback loop, masking that thousands of real orders are being placed and shipped.