Billing

Credit Units

• 1 USD = 1000 credits
• minimum charge: 1 credit
• rounding: ceil(...)

Ledger Model

Platform keeps immutable ledger entries:

• hold_create
• hold_release
• charge
• topup (payment)
• refund (future)

Atomic Flow

• pre-check available credits
• create hold in transaction
• call upstream
• finalize or release hold in transaction

u2 Duration Formula

Current retail formula:

• retail_cny_per_sec = 0.00008 * 12 = 0.00096
• total_usd = (duration_sec * 0.00096) / 7.2
• credits = max(1, ceil(total_usd * 1000))

Submit hold cap defaults to 80 credits.