ATM we have two memory caching Persistence handler implementations, Language and ContentType. These cache data in-memory, meaning for the lifecycle of their services. They are located in Legacy Storage Engine (LSE), and are configured in main LSE handler, using concrete implementations to do their job. This also means Cache storage ends up using them in its implementations.
There are several problems with this setup:
1. there is nothing specific to LSE in their implementations
2. when Cache Storage Engine is configured to work with LSE, logic in Cache handler implementations will override their function and in-memory cache will be created, but never hit, so they are basically dead weight now
Move memory caching handlers into Cache storage and configure them with concrete Cache handler implementations. Here they can actually be put to good use, avoiding unnecessary hits on SPI (Stash) cache.