Shopify Replaces Redis with MySQL for High-Volume Inventory Reservations and Scales Production

In a detailed engineering architecture report, Shopify revealed how its core infrastructure team successfully migrated high-volume flash sale inventory reservations from Redis back to MySQL. While Redis is widely favored for in-memory caching, Shopify found that during peak Black Friday sales events, maintaining strict ACID guarantees and dual-write consistency between Redis caches and primary databases created complex distributed consensus bottlenecks. By implementing row-level locking optimizations, custom batching algorithms, and memory-mapped temp tables directly within MySQL, Shopify achieved throughput exceeding 100,000 reservation transactions per second per database shard with zero inventory overselling.