By default, WordPress handles all content types—posts, pages, attachments, and WooCommerce orders—inside a single, shared database table called wp_posts. Because of this unified database schema, your order identification numbers are non-sequential. Order #1002 might be followed immediately by Order #1003, but if a shop manager creates a new blog post, the next transaction automatically becomes Order #1005.

A severe database index bug occurs when custom plugins attempt to force a sequential order numbering system (e.g., custom prefix numbering layouts). If a database crash occurs, or if auto-increment pointer configurations get out of sync during bulk order deletions, WooCommerce can attempt to assign a newly created transaction an ID string that has already been taken by an existing order record. The database query fails due to a key collision constraint, throwing a fatal error at checkout and blocking all new sales.

The Solution

Resolving order key collision bugs requires correcting database sequence indices or migrating your store layout engine to use dedicated tables.

  1. Enable High-Performance Order Storage (HPOS): The ultimate, permanent fix for order storage conflicts is migrating your data engine away from the legacy shared wp_posts layout entirely. Navigate to WooCommerce > Settings > Advanced > Features and activate High-Performance Order Storage. This separates order indices into their own dedicated, unshared database structures.

  2. Reset Database Auto-Increment Counters: If your site continues to drop transactions due to ID allocation overlap loops, access your site database via phpMyAdmin, open the SQL query execution tab, and enter this index realignment script command:

    SQL
     
    ALTER TABLE wp_posts AUTO_INCREMENT = 50000;

    (Note: Set the target integer configuration number to an absolute value safely above your highest active order number indicator).

  3. Disable Outdated Sequential Plugins: Audit your active plugins list. Deactivate any legacy custom order number modification extensions that rely on filtering post tracking parameters manually through volatile PHP arrays.