# What is WAL backpressure, and why does ClickHouse Managed Postgres need it?

DevFeed: [What is WAL backpressure, and why does ClickHouse Managed Postgres need it?](<https://devfeed.tech/articles/what-is-wal-backpressure-and-why-does-clickhouse-managed-postgres-need-it-5629.md>)

Original publisher: [Read original article](<https://clickhouse.com/blog/wal-backpressure-clickhouse-managed-postgres>)

Author: Kaushik Iska

Published: 2026-08-05T15:58:59Z

Content type: article

Language: en

Sources: [ClickHouse Blog](<https://devfeed.tech/sources/clickhouse-blog.md>)

Topics: [clickhouse](<https://devfeed.tech/topics/clickhouse.md>), [Database](<https://devfeed.tech/topics/database.md>), [systemd](<https://devfeed.tech/topics/systemd.md>), [Amazon EC2](<https://devfeed.tech/topics/amazon-ec2.md>), [benchmarking](<https://devfeed.tech/topics/benchmarking.md>), [Processes](<https://devfeed.tech/topics/processes.md>), [Ubuntu](<https://devfeed.tech/topics/ubuntu.md>)

Tags: [backend](<https://devfeed.tech/tags/backend.md>), [benchmark](<https://devfeed.tech/tags/benchmark.md>), [clickhouse](<https://devfeed.tech/tags/clickhouse.md>), [database](<https://devfeed.tech/tags/database.md>), [process](<https://devfeed.tech/tags/process.md>), [scale](<https://devfeed.tech/tags/scale.md>), [storage](<https://devfeed.tech/tags/storage.md>), [systemd](<https://devfeed.tech/tags/systemd.md>), [ubuntu](<https://devfeed.tech/tags/ubuntu.md>)

## AI overview

ClickHouse Managed Postgres uses WAL-aware backpressure to prevent a full WAL disk from causing an outage. A systemd timer measures pending WAL segments and applies increasingly strict cgroup v2 I/O limits to client backends while leaving the archiver, checkpointer, logger, and all reads uncapped. A benchmark on an EC2 instance demonstrates the mechanism under a deliberately rate-limited object store and a backed-up archiver.

## Source excerpt

How ClickHouse Managed Postgres uses WAL-aware backpressure to slow client writes, protect disk space, and let the archiver recover.