WooCommerce: variations data layer (CRUD + cache)

For plugin code that reads, queries, or programmatically writes product variations. The pricing/display side (filter chain, sale-price overrides, frontend "Variation X is selected" hooks) is sibling skill wc-variations-pricing-filters — this one stops at the data layer.

Misconception this skill corrects

"A variation is just a product. I'll wp_insert_post( 'product_variation', ... ) and update_post_meta for price."

Variations work that way at the database level, but the data layer caches aggressively at the parent level. A raw post-insert leaves the parent's stored _price values, lookup table row, child-list transient, and wc_var_prices_<id> transient stale — your variation exists but the catalog shows the OLD price range, "Out of stock" stays on a re-stocked variable product, and frontend variation data may not see the new child until caches are rebuilt.

When to use this skill

Trigger when ANY of the following is true:

• Programmatically creating, updating, or deleting variations (import scripts, sync from external system, CLI tools).
• Reading variation prices for catalog display, custom listings, or reports.
• Debugging "I added a variation programmatically and the parent's price range / stock didn't update".
• Reviewing code where variations are touched via wp_insert_post, wp_update_post, update_post_meta, or raw $wpdb writes against product_variation post type.
• The diff or file contains: WC_Product_Variation, WC_Product_Variable, get_variation_prices, get_available_variations, wc_var_prices_, sync_variation_names, or 'product_variation' post type references.