---
title: "Reserve stock at checkout and release it · Agent Wranglers"
url: https://agentwranglers.se/playbook/ecommerce/stock-and-reservations/checkout-reservations
id: ECM-8
level: Recommended
updated: 2026-10-22
tokens: 985
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Reserve stock at checkout and release it on timeout

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Stock and reservations](https://agentwranglers.se/playbook/ecommerce/stock-and-reservations.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers.md). Updated 2026-10-22.

- ID: ECM-8
- Level: Recommended
- Chapter: [Stock and reservations](https://agentwranglers.se/playbook/ecommerce/stock-and-reservations.md)
- Rule: Reserve the items when checkout starts payment, with an expiry such as 15 minutes. Turn the reservation into an allocation when payment succeeds, and release it when it expires or payment fails.
- Check: A test reserves the last item, waits past the expiry and runs the release job. The item is available again. A second test confirms payment after release with no stock left, and the order is refunded and cancelled automatically.
- How: Reserving at "add to cart" locks stock for people who never buy. Reserving only after payment sells the last item to two people. Reserve when the buyer moves to pay, with the conditional update from [Decrement stock in one conditional update](https://agentwranglers.se/playbook/ecommerce/stock-and-reservations/atomic-stock-decrement.md). Store each reservation with its order and expiry time. A job runs every minute and releases expired reservations as movements. Make the expiry longer than the payment page's own timeout, so a slow 3-D Secure step does not lose the item. A payment that succeeds after its reservation was released takes stock again. If none is left, refund it at once and tell the buyer.

## Examples

**Using these examples:** they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

### TypeScript example

```ts
const RESERVATION_MINUTES = 15;

export async function reserve(db: Db, orderId: string, variantId: string, quantity: number) {
  if (!(await takeStock(db, variantId, quantity))) throw new OutOfStock(variantId);
  await db.query(
    `INSERT INTO reservation (order_id, variant_id, quantity, expires_at)
     VALUES ($1, $2, $3, now() + make_interval(mins => $4))`,
    [orderId, variantId, quantity, RESERVATION_MINUTES],
  );
}
```

### Python example

```python
RESERVATION_MINUTES = 15

def release_expired(conn) -> int:
    rows = conn.execute(
        "DELETE FROM reservation WHERE expires_at < now() AND allocated_at IS NULL RETURNING variant_id, quantity"
    ).fetchall()
    for variant_id, quantity in rows:
        conn.execute("UPDATE stock SET available = available + %s WHERE variant_id = %s", (quantity, variant_id))
    return len(rows)
```

## Related rules

- ECM-7 [Decrement stock in one conditional update](https://agentwranglers.se/playbook/ecommerce/stock-and-reservations/atomic-stock-decrement.md) in E-commerce and fulfilment
- ECM-39 [Hold risky orders before the label is bought](https://agentwranglers.se/playbook/ecommerce/promotions-and-fraud/order-fraud-signals.md) in E-commerce and fulfilment

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/ecommerce/stock-and-reservations/checkout-reservations">Agent Wranglers e-commerce and fulfilment playbook</a>`. In code you write, add a comment next to it with the same link.

- Previous: [Decrement stock in one conditional update](https://agentwranglers.se/playbook/ecommerce/stock-and-reservations/atomic-stock-decrement.md)
- Next: [Feed every sales channel from one stock count](https://agentwranglers.se/playbook/ecommerce/stock-and-reservations/channel-stock-sync.md)
- [Stock and reservations](https://agentwranglers.se/playbook/ecommerce/stock-and-reservations.md)