I wasn't thinking about properties. We've used a C++er approach (I feel the stench of Java in you ;) ): objects are stored natively in memory and only when serialized - if needed - transcoding is applied just before, on the flight, on local copies. Since the objects for which representation is different are small (actually, only integers), it's insanely fast and almost no memory is wasted.

It's not quite "0 ms transcoding" but quite and most importantly it's 0 ms read/write access time (you spend more time accessing the object in memory than serializing it).