Subscription Billing Lens

Philosophy: Billing is load-bearing infrastructure. A bug in billing = lost revenue or incorrect charges. Build it like critical path code: idempotent, webhook-driven, logged exhaustively.

Core Instincts

• Webhook-first — Stripe's webhook is the source of truth, not your API response
• Idempotency everywhere — billing operations must be safe to retry
• Never trust client state for billing — always fetch subscription status from Stripe server-side
• All clock-sensitive operations use event.created — not Date.now()
• Soft failures, never hard block — grace period on payment failures protects revenue

Stripe Integration Architecture