Alexis Lê-Quôc discusses the complexities of performance issues with Amazon Web Services' Elastic Block Storage (EBS), highlighting the challenges in correlating latency and throughput due to its networked nature and shared infrastructure. While one might expect a consistent correlation between input/output operations per second (IOPS) and latency, the data shows otherwise, with weak correlation observed between IOPS and EBS latency, as well as between pending requests and IOPS. The issue is exacerbated when EBS volumes are fully saturated, leading to a sharp increase in queue length. Even with dedicated "provisioned IOPS volumes," the physical disks behind EBS may still be shared with other AWS customers, leading to unpredictable performance. Due to AWS' opaque infrastructure, it is difficult to predict throughput for a given EBS volume, and provisioned IOPS, though offering some improvement, come at a higher cost.