ClickHouse's WalShadow replicates Postgres to ClickHouse in 200 ms from physical WAL

WalShadow: Sub-second Postgres replication to ClickHouse from physical WAL

ClickHouse has open-sourced WalShadow, an engine that replicates Postgres data to ClickHouse directly from physical WAL. In benchmarks, committed transactions became visible in ClickHouse in about 200 ms, and WalShadow sustained 289K rows/sec, matching the source Postgres instance. Unlike traditional CDC systems, it avoids logical replication slots, decodes WAL outside the source, and writes ClickHouse-native blocks. It supports initial load, continuous replication, schema evolution, restart recovery, and switchovers. A managed version is in private preview for ClickHouse Managed Postgres.