Put Prepaid Units Ahead of Metered Charges - Ruba Docs

Credits are prepaid units attached to a Usage Meter. When an event reaches that meter, Ruba consumes the customer’s available units before applying the product’s metered price to any remaining usage.

Balance sequence

Your application sends an event to a Usage Meter.
Ruba evaluates the usage against the customer’s meter balance.
Available credits are consumed first.
After the balance reaches zero, further usage becomes billable overage when the product has a metered price.

If you want a strict credits-only product with no Ruba overage charge, leave the product without a metered price for that meter.

Add credits through a benefit

Create a Usage credits benefit, choose its meter, and define the number of units. Delivery timing follows the product type:

Ruba benefit form configured for Usage credits in light mode

Ruba benefit form configured for Usage credits in dark mode

Product	When units arrive
Monthly or yearly subscription	At the beginning of every billing cycle
One-time product	Once, when the purchase is completed

Read and enforce the balance

Customer State returns the customer’s active meter balances with the rest of their access state. Use the Customer Meters API when you only need meter balances.

A zero balance does not make Ruba block your application’s feature. Your application must reject or limit usage when that is the intended product rule.