Datomic is a proprietary database management system. It is an operational DBMS, in other words, it allows updates in real time. Instead of assigning and overwriting values into named attributes, Datomic keeps track of all immutable facts over time, which sets Datomic apart because previous states can be accessed easily. Datomic is also a distributional DBMS, which provides horizontal read scalability. Therefore, Datomic is a good fit for storing a history of valuable records that requires operational flexibility and read scalability. In addition, Datomic Cloud is built for AWS integration and is a quicker and easier way to access Datomic on AWS.
Early March 2012, the Relevance team (later joined with Metadata to form Cognitect) around Rich Hickey released Datomic, which they have started to work on since 2010.
Datomic treats storage as a service, which means that Datomic only provides the ways to access underlying storage, but doesn't provide the actual storage.
Stored procedures are represented as "transaction functions" in Datomic.
Datomic indexes are covering indexes. In other words, instead of storing reference to data in the index, Datomic directly reads data from index.
Datomic stores immutable facts as datoms over time. A datom follows the form of `(entity, attribute, value, time).`
Each "peer" in Datomic that communicates with storage services and transactors has its own cache.
Index trees contain "segments," arrays of datoms that are serialized and then compressed with zip. Compression allows more efficient caching and storage.
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