Behavior of HistoryService if history data is stored externally

Following the examples here at,
it is possbile to configure history data to be stored in an external database.

Does this make HistoryService unusable? I cannot find how we can route HistoryService to fetch data externally.
In this scenario, how should HistoryService behave?

There is indeed no out of the box implementation for an external data store (as there are many possible stores).
It is possible to inject your own implementation of the HistoryService into the processEngineConfiguration though, based on whatever store you’ve picked.