Preventing Overselling with Stock Reservation and select_for_update in Django

Short summary

A Django developer explains how to prevent overselling in e-commerce by separating real stock from reserved stock, using database-level row locking via select_for_update(). During checkout, only reserved_stock is incremented; actual stock decreases only after payment confirmation. The approach uses consistent lock ordering via order_by('id') to avoid deadlocks and a single bulk_update for efficiency.

• •Separate stock into real stock and reserved_stock to avoid premature decrements during checkout
• •Use select_for_update() with order_by('id') to lock rows and prevent deadlocks
• •Decrement real stock only after payment confirmation via webhook, not at checkout start

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