I didn't realise you were open to the idea of using an integrable store. I can check if any of the existing in memory stores are 1) stable enough, 2) do what we want and 3) have a license we can use.
Though I also think, our use case is so application specific, we really don't need all the bloat a generic store will come with, as they try to be generic, by definition. It might be interesting to measure how using such a store performs or if they are usable at all.