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.