# QuotaStack Documentation
# https://quotastack.io
# Machine-readable index for LLMs and AI agents

## Concepts
- [Credits](/docs/concepts/credits.md): How credits are stored, granted, debited, and tracked using millicredits, credit blocks, and an append-only ledger.
- [Entitlements](/docs/concepts/entitlements.md): How to check whether a customer can perform an action, with Redis caching for fast hot-path checks.
- [Metering](/docs/concepts/metering.md): How to define billable metrics, configure pricing rules, and record usage events that debit credits.
- [Reservations](/docs/concepts/reservations.md): How to hold credits during long-running operations using reserve/commit/release lifecycle.
- [Topups and Wallets](/docs/concepts/topups-and-wallets.md): How to grant credits after payment, model wallets and credit packs, and control burn order.
- [Subscriptions](/docs/concepts/subscriptions.md): Recurring billing state management with prepaid/postpaid modes, credit grants, and rollover.
- [Idempotency](/docs/concepts/idempotency.md): How duplicate operations are prevented using the Idempotency-Key header and advisory locks.
- [Webhooks](/docs/concepts/webhooks.md): Event delivery with HMAC-SHA256 signing, retry schedule, and event catalog.