I'm sticking with the ConcurrentDictionary as I need to store data from database for each user and I prefer it because its thread safe.

So my question. If I use a static ConcurrentDictionary<int, List<T>> this will be stored in memory? I have also read some articles about AppFabric which can be used for distributed caching but unfortunately support for AppFabric is minimal yet. I cannot even find a book to buy for programming with appfabric.