Oracle TimesTen - TimesTen is an in-memory, relational database management system with persistence and...
Datahike - A durable datalog database adaptable for distribution.
Datomic - The fully transactional, cloud-ready, distributed database
MarkLogic Server - MarkLogic Server is a multi-model database that has both NoSQL and trusted enterprise data management capabilities.
PlanetScale - The last database you'll ever need. Go from idea to IPO.
Matisse - Matisse is a post-relational SQL database.