The 2nd edition maintained PostgreSQL, MongoDB, Neo4j, and Redis, acknowledging their continued relevance and evolution. It substituted others to better reflect the changing landscape:
RethinkDB (Document/Realtime): Replaced Riak and CouchDB, showcasing a document database with real-time push capabilities. (Note: RethinkDB later ceased commercial operations, highlighting the volatility of the NoSQL landscape).
MongoDB
Cassandra (Column-Family): Replaced HBase, reflecting Cassandra's growing morocco phone number list enterprise adoption due to its always-on architecture and impressive scalability.
Datomic (Immutable/Time-Travel): A highly innovative and unique database with an immutable data model, allowing "time-travel" queries and strong consistency guarantees. Represented a cutting edge in database design.
The shifting lineup between editions underscores the dynamic nature of the database world and the book's commitment to presenting relevant technologies.