Usage-Based Billing on Stripe Silently Double-Charges Customers — No Built-In Duplicate Detection or Anomaly Alerting

Summary

Indie SaaS founders who bill on usage push daily aggregated events to Stripe as usage records. When an aggregation job times out and the scheduler retries it, Stripe has no concept of the duplicate — it simply sees 'more usage' and bills the customer a second time. In the reported case this went undetected for two days, produced internally 'correct-looking' invoices that were fundamentally wrong, cost 31 customers a double charge, $6,200 in refunds, and an enterprise account now demanding manual usage exports to re-verify every bill. The killer detail: 'nothing was alerted, no errors or failed jobs.' Stripe's fixed-price subscription protection does not extend to metered/usage-based billing, so the entire burden of idempotency, deduplication, and pre-finalization anomaly detection falls on each founder to reinvent. There is no drop-in monitoring or guardrail layer that watches usage records flowing into Stripe, flags customers whose usage jumps abnormally before invoices finalize, and blocks replayed retries — a huge, unsolved, high-commercial-value opportunity for an indie developer targeting the exploding usage-based SaaS market.