We replaced Redis with MySQL for inventory reservations—and it scaled (2026) - Shopify

We replaced Redis with MySQL for inventory reservations—and it scaledHow we used SKIP LOCKED, composite primary keys, and connection visibility to hit our scale targets. During checkout, when a buyer clicks "Complete purchase," we need to guarantee the items they're buying are still available. If we get this wrong in one direction, two buyers purchase the same last unit: the merchant has to cancel

[mkusaka]

Shopifyが在庫予約の保存をRedis→MySQLへ移行し、SKIP LOCKEDと複合主キーでスケールを実現した解説記事です。

[dd41kk]

1単位を1行で管理して SKIP LOCKED で オーバーセルを防止して在庫バッファでパフォーマンスを担保。一気にRedisからMySQLに切り替えず、シャドウモード（ダークローンチ）で並行稼働して問題無いことを確認した後に切り替え