Failure handling releases resources

A failed payment that leaves a PENDING_PAYMENT or HELD booking blocks the slot indefinitely: the booking appears in capacity counts, the slot shows as unavailable to other users, and the original customer cannot retry because the slot appears taken. CWE-459 (incomplete cleanup on error) names this pattern precisely. Every payment failure path — declined card, network timeout, webhook failure — must release both the booking status and the slot hold atomically. A slot left blocked by a failed payment is functionally equivalent to a permanently deleted slot from the user's perspective.

Handle payment failures in your Stripe webhook handler (e.g., src/app/api/webhooks/stripe/route.ts) with an atomic transaction that updates both the booking and the slot.

// In payment_intent.payment_failed webhook handler
const bookingId = event.data.object.metadata.bookingId;
const booking = await db.booking.findUniqueOrThrow({ where: { id: bookingId } });

await db.$transaction([
  db.booking.update({
    where: { id: bookingId },
    data: { status: 'FAILED', failureReason: 'payment_declined' }
  }),
  db.slot.update({
    where: { id: booking.slotId },
    data: { bookedCount: { decrement: 1 } }
  }),
]);