Building a 2KB Histogram with Sub-0.2% Percentile Error

The Problem: Tracking Request Latency Without Slowing Things Down For a cloud data warehouse, performance is not just about average query time. What often matters more is tail latency, predictability, and the ability to pinpoint where things go wrong. In a cloud-native data warehouse like Databend, a single request may pass through multiple stages: SQL planning, distributed execution, remote storage, Raft logging , and state machine apply.