WalShadow is an open-source engine that replicates Postgres data to ClickHouse directly from physical WAL, achieving sub-second latency (around 200 ms) and sustaining 289K rows/sec throughput. It eliminates logical replication slots and operational overhead by consuming the same physical WAL stream used by Postgres replicas, decoding it externally, and writing ClickHouse-native blocks directly. ClickHouse is also launching WalShadow in private preview for its managed Postgres service.
Walshadow is an experimental tool that replicates PostgreSQL rows into ClickHouse using physical WAL, supporting initial load, continuous changes, and schema evolution. It requires PostgreSQL 16+ and is currently in development preview with interfaces subject to change.