As can be seen in https://github.com/ezsystems/ezpublish-kernel/blob/23b52c1d361060e463f7afd8f3a6cca3a1fb5efe/eZ/Publish/API/Repository/Tests/SetupFactory/LegacySolr.php, Solr search handler can use SPI cache handlers.

However this is achieved using reflection and not yet possible to configure in the container, as fetching cached handler dependencies depends on the main storage handler, which in turn depends on the search handler, therefore creating circular dependency.

This is quite important from performance POV and needs to be solved in some way, possibly using a factory to get (cached) storage handlers.

The possibility to move search out of persistence was mentioned and this could also be solved as a part of that effort.