How can I implement caching layer in Android with sqlite database?

I am implementing android chat/messenger application. Wherein I want to show chats between multiple participant. User may switch chat windows very frequently.

I am using sqlite for persistent storage. But reading data very frequently from sqlite seems little expensive. So I want to use in memory data caching in my android app. And I would like to keep recently accessed chats there.

Hashmaps and arraylists are becoming very complicated as I need 4-5 attributes to access the objects of Class as key.

I was thinking of using something like Google's guava. Or some another MultiKey data-structure. Please suggest good option.