Silent Data Loss in ClickHouse: 3 Reasons Your Distributed Queue Keeps Growing

Inserts into ClickHouse Distributed tables seem to succeed instantly but silently pile up as .bin files in an on-disk queue that never reaches the underlying ReplicatedMergeTree tables, causing permanent data loss and missing rows. The root causes include ClickHouse Keeper downtime putting replicas into read-only mode and stalling background flushes, as well as oversized insert blocks killing the flush and blocking the entire queue.