MemSQL is a scale-out distributed, relational database, with a lock-free architecture that supports both row and column storage. The former is used in-memory for OLTP, while columnar data is disk-based and supports analytics.
As far as developers and users are concerned MemSQL is a traditional relational database and brings all the advantages that you would expect from that familiarity. And the wire compatibility with MySQL is a major advantage for anybody looking to migrate from an incumbent relational supplier. More significantly, MemSQL reverses the use of memory and disk storage with respect to rows and columns, compared to the traditional relational vendors who had no choice in the matter. This means that you can get better performance for transaction processing while using fewer hardware resources, while maintaining low latency for analytics and query processing.