MySQL's Hidden I/O Bottleneck: When Synchronous Writes Meet NVMe Queues

MySQL's doublewrite buffer relies on synchronous writes, creating a critical bottleneck when NVMe hardware queues saturate during concurrent workloads. Even on capable hardware offering 600,000 IOPS and sub-millisecond latency, this synchronization overhead degrades write performance to 85+ milliseconds. The insight matters because the actual bottleneck isn't throughput capacity but write ordering guarantees and queue management—a lesson in storage architecture that extends beyond MySQL.