There is another database which can be used in the 'accumulation-based' space: http://geteventstore.com http://geteventstore.com It has the same main drawbacks

There is another database which can be used in the 'accumulation-based' space: http://geteventstore.com http://geteventstore.com It has the same main drawbacks as Datomic - it's young and multi-node deployment comes with commercial plan only, however it's really fast and easy to work with once you embrace the event-sourcing programming model.