I feel like a lazily loaded datastructure would solve this problem - you only need the last k transactions, then it only loads the last k transactions...
With regard to Om or Clojure I'm not sure of the specifics of such an implementation, but doing something like that with other languages that have functional programming support is one of the Major Selling Points.
With regard to Om or Clojure I'm not sure of the specifics of such an implementation, but doing something like that with other languages that have functional programming support is one of the Major Selling Points.