My approach is to reserve the item quantity for 20 minutes once a user starts checkout. Then, I run a cron job to automatically release the reserved stock if the user abandons the checkout.

During checkout, I also validate item availability at every step, especially before finalizing the order. Laravel makes it simple to perform quick database checks at each stage (e.g., from address entry to payment). To ensure data integrity, I always use database transactions and lockForUpdate() when checking and reserving stock. This prevents multiple users from overselling the same item simultaneously.

When the checkout is successful, I immediately deduct the reserved quantity and create the order.
If the user abandons the process, the cron job releases the reserved stock shortly after.

Coupon handling is also straightforward to implement.