[hcarvalhoalves]

From what I gather, underneath Datomic is an event sourcing database, which is a model that already scales "for free".

Further optimization is the fact the query engine lies on the application, so if you have N application servers you have N CPUs available for querying - as opposed to overloading a master server or having to provision read slaves.

[cordite]

It can be used for event sourcing, but it does prune past data (for single-value values, compared to set-like values) in the current database indexes. Old data is still available in older indexes.