Terracotta provides a highly available, highly scalable persistent to disk object store. You can use it for just this feature alone - or you can use it's breadth of features to implement a fully clustered application - your choice.
Terracotta:
- does not break object identity giving you the most natural programming interface
- does not require Serialization
- clusters (and persists) nearly all Java classes (Maps, Locks, Queues, FutureTask, CyclicBarrier, and more)
- persists objects to disk at memory speeds
- moves only object deltas, giving very high performance
Here's a case study about how gnip uses Terracotta for in-memory persistence - no database. Gnip takes in all of the events on Facebook, Twitter, and the like and produces them for consumers in a normalized fashion. Their current solution is processing in excess of 50,000 messages / second.
It's OSS and has a high degree of integration with many other 3rd party frameworks including Spring and Hibernate.
