[vadman97]

Once we hit >100k inserts per second, async inserts didn't work well for us because we had limited control over the background async insert batching happening on the cluster. The background inserts would be too small, resulting in many merges running, causing high CPU, causing high back-pressure (latency) on async inserts which would just result in an ingestion delay.

Plus, async inserts are only available on ClickHouse Cloud.

[zX41ZdbW]

Asynchronous INSERTs are available in the open-source ClickHouse version and in ClickHouse Cloud. The feature is independent of the Cloud.

To enable asynchronous INSERTs, set `async_insert` to true.

Here is the documentation: https://clickhouse.com/docs/en/optimize/asynchronous-inserts ; intro: https://clickhouse.com/blog/asynchronous-data-inserts-in-cli... and a hands-on guide: https://clickhouse.com/blog/monitoring-asynchronous-data-ins...

[dilyevsky]

Like sibling comment is saying - async inserts are part of the oss version. Batch flushes are tunable in two dimensions - size and latency. I think it’s likely the default size was just too low for your usecase

[vadman97]

Forget the exact details, but we ran into issues with tuning the two setting you're describing on the Cloud instance (these settings were user level settings that seemed to get reset by ClickHouse Cloud because they were updated based on the cluster size). Perhaps this could change with Cloud and isn't an issue with the OSS version.