Shopify Swaps Redis for MySQL in Inventory System, Achieves Better Scalability

Shopify has replaced Redis with MySQL for its inventory reservation system, which handles the temporary holding of stock during payment processing for millions of daily orders. The engineering team found that Redis, while fast, introduced operational complexity by requiring two data stores to stay in sync and offering weaker durability guarantees compared to MySQL's ACID compliance. By leveraging MySQL InnoDB's row-level locking and the SKIP LOCKED feature introduced in MySQL 8.0, Shopify was able to handle high-concurrency reservation operations without the overhead of maintaining a separate Redis cluster. The migration reduced infrastructure complexity and cost while meeting the strict consistency and throughput demands of peak shopping events like Black Friday. The move challenges the common assumption that Redis is always the superior choice for high-throughput, low-latency backend operations.