Memcached is just a cache. The out of box java version at https://code.google.com/p/quickcached/ supports writing to disk on exit but for what you need, I think you will have to add your own code.

One thing to consider is how much of data, at peak load do you think you will have 3 years from today? If that is not too much can use your own RAM with a in memory cache like whirly, and your own thread that peeks in the to cache every 5 minutes and saves to disk items that are not yet picked up. Not your POJO will have to have the checked in time, whirly wont tell you when an item was put into its cache.

Memcached is just a cache. The out of box java version at https://code.google.com/p/quickcached/ supports writing to disk on exit but for what you need, I think you will have to add your own code.

One thing to consider is how much of data, at peak load do you think you will have 3 years from today? If that is not too much can use your own RAM with a in memory cache like whirly, and your own thread that peeks in the to cache every 5 minutes and saves to disk items that are not yet picked up. Note: your POJO will have to have the checked in time, whirly wont tell you when an item was put into its cache.