There is another place where you should not use CH, and it's in a system with shared resources. CH loves, and earned the right, to have spikes of hogging resources. They even allude to this on the Keeper setup - if you put the nodes for the two systems in the same machine, CH will inevitably push Keeper off the bed and the two will come to a disagreement. You should not have it on a k8s Pod for that reason, for example. But then again, you shouldn't have ANY storage of that capacity in a k8s pod anyways.

DuckDB probably performs better per core than clickhouse does for most queries. So as long as your workload fits on a single machine (it's likely that it does) it's often the most performant option.

Besides, it's so simple, just a single executable.

Of course if you're at a scale where you need a cluster it's not an option anymore.