Credits / Wallet
A prepaid balance that usage burns down over time. Wallets can hold paid credits, promotional grants, and trial credits separately.
A credit wallet is a prepaid balance that usage burns down over time — instead of being billed after the fact for what was consumed, an account holds a balance upfront, and every unit of usage deducts from it. It's the default pricing primitive for AI products specifically, because token- and inference-based costs are naturally usage-shaped and customers want to see a balance rather than an open-ended bill.
Wallets aren't just one number. A single wallet typically needs to track more than one kind of balance at once — credits a customer paid for, and free credits granted for a trial or promotion — and the two shouldn't be treated the same way. Well-designed wallets burn promotional and trial credits before paid ones, so a free trial allowance doesn't quietly eat into money a customer actually spent.
The other design problem is timing: what happens when a balance gets close to zero? A wallet that only reacts after it's already empty creates the exact failure mode usage-based products fear most — a mid-request or mid-batch-job stoppage. A wallet built to alert or auto-top-up at a threshold, before hitting zero, avoids that entirely.