You'll have to identify every way in which your data can change and create your solution accordingly. Any class could work as an in-memory cache as long as you register it as a singleton. You can use the pub-sub pattern (https://www.enjoyalgorithms.com/blog/publisher-subscriber-pattern) to eagerly populate your cache based on events in your application. You can use Query Notifications in Sql server (https://learn.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms175110(v=sql.105)) to notify your code of changes in the database and update your cache accordingly on each instance. Umbraco already provides so-called notification handlers for the pub-sub pattern which you can use.