Stripe Integration for SaaS Products

The part of SaaS billing that breaks in production is almost never the initial checkout — it's everything that happens after. Plan changes mid-cycle need proration handled correctly in both directions (upgrade and downgrade), failed renewal payments need a dunning sequence that doesn't just cancel a customer on the first decline, and self-serve plan changes need to respect any commitments (annual contracts, seat minimums) you've layered on top of Stripe's defaults.

Where SaaS Billing Architectures Usually Go Wrong

• Prorating upgrades correctly but not downgrades, leaving credit balances that never reconcile
• Treating a failed card as an immediate cancellation instead of a retry-then-dunning sequence
• Hardcoding seat counts instead of using metered/usage records, breaking the moment pricing changes
• No webhook handling for `customer.subscription.updated`, so your app's plan state silently drifts from Stripe's

We build the subscription lifecycle state machine explicitly — trial, active, past_due, canceled, and every transition between them — rather than letting it emerge from whatever webhooks happen to arrive first. That's the difference between a billing system that survives a Stripe outage or a customer's expired card, and one that quietly corrupts subscription state under exactly those conditions.