Shopify Replaced Redis with MySQL for Inventory Reservations, Scaling for Peak Traffic

Migration to MySQL for Inventory Reservations

Shopify has transitioned its inventory reservation system, critical for preventing overselling during checkout, from Redis to MySQL. This migration was part of a broader initiative to consolidate database technologies within the company. The previous Redis-based system handled inventory holds during payment processing.

Addressing Scaling Challenges with MySQL

Earlier attempts to use MySQL for this function failed due to contention issues with a single row per item design. The successful implementation leveraged MySQL 8's SKIP LOCKED feature and adopted a design with one row per inventory unit. This approach allowed the system to meet high-throughput targets during peak traffic events.

Impact on Peak Sales Performance

The new MySQL-based reservation system demonstrated its capability during Black Friday 2025, when Shopify's platform processed a record $5.1 million in sales per minute at its peak. This performance is crucial for Shopify, which powers over 14% of U.S. e-commerce, ensuring that inventory is accurately reserved and claimed without errors or slowdowns.

Importance of Oversell Protection

Oversell protection is vital for e-commerce platforms to prevent negative customer experiences and lost revenue. The system ensures that items are marked as reserved when payment begins and permanently deducted from inventory upon successful payment. Fast and correct operation of this system is essential to avoid throttling, overselling, or underselling.