Unlike traditional RDBMSs, the Datomic Architecture separates storage, transactions, and query. Datomic’s data model is based upon a universal primitive relation, of datoms, rather than an arbitrary set of named relations. The query model, while relational, is based upon Datalog, not SQL. Datomic has weaker constraint capabilities than some RDBMS, but more flexible data modeling. It shares ACID transactions and arbitrary joins.
Most NoSQL databases sacrifice transactionality and join capability and adopt sharding and eventual consistency. They also often have data models not supported by relational logic. Datomic trades off arbitrary write scalability to retain arbitrary transactions and joins. It provides a strong data model and powerful query with arbitrary read and query scaling.