"10 Stripe Billing Anomalies I Monitor in Real-Time (And the Code Behind Each One)"

10 Stripe Billing Anomalies I Monitor in Real-Time (And the Code Behind Each One) After losing $800 in MRR to a silent charge failure cascade that went unnoticed for 4 days, I built BillingWatch — a self-hosted Stripe webhook monitor with 10 real-time anomaly detectors. Here's exactly how each one works. The Architecture: Event-Triggered, Not Scheduled The critical design choice: detectors run on every Stripe webhook event, not on a cron schedule. Cron-based checks have a window problem — you might miss a 5-minute card testing attack. Event-triggered detection means you catch it within seconds of the first anomalous event. @app.post ( " /webhook " ) async def stripe_webhook ( request : Request , db : Session = Depends ( get_db )): payload = await request . body () sig_header = request . headers . get ( " stripe-signature " ) event = stripe . Webhook . construct_event ( payload , sig_header , WEBHOOK_SECRET ) store_event ( event , db ) await run_detectors ( event , db ) return { " statu