Balances

Balances, caps and overage

• A balance counts down to 0. Going below 0 is overage.
• Two things let usage go past 0, and nothing else does:
  • a usage-based price on the plan item — they go over and get billed for it.
  • the overage_allowed billing control.
• If neither is set, included IS the cap: usage stops at 0 and check returns allowed: false. Nothing extra is needed to enforce it.
• So never add a spend_limit to "cap" a feature that has no overage price and no overage_allowed — it is already capped, and the limit does nothing.

How controls interact with balances

• Only overage_allowed changes whether usage may pass 0. The rest just bound usage that is already permitted.
• usage_limits: a separate gate on TOTAL usage per time window, counted independently of the balance. This one bites whether or not overage exists, and can sit below the included amount.

Tracking past zero