What I Learned from a Month with WalShadow on ClickHouse Managed Postgres
ClickHouse, Friday, November 6th, 2026
A database engineer tested ClickHouse's managed WalShadow for a month, comparing its Postgres replication latency and correctness with ClickPipes.
Hidehiko Asahi, a database engineer in Japan and AWS Community Builder, tested the managed WalShadow in ClickHouse Managed Postgres during its private preview in September and October 2026.
The Sync to ClickHouse wizard offers ClickPipes, which uses Postgres logical replication and works with sources like RDS and Cloud SQL, and WalShadow, which decodes physical WAL outside Postgres and writes blocks directly to ClickHouse.
WalShadow is possible because ClickHouse manages both sides, and it is recommended for the lowest latency and replication overhead.
Asahi compared the two on a 16 vCPU source for latency, checked data correctness and examined schema changes and recovery, noting results may change before general availability.