MemSQL is s fast, commercial, ANSI SQL compliant, highly scalable HTAP database. HTAP databases are those that support both OLTP and OLAP workloads. It supports ACID transactions just like a regular relational database .It also supports document and geospatial data types.
MemSQL is fast because it stores data in-memory. But, it does not mean it is not durable. It maintains a copy of data on disk as well. Transactions are committed to the transaction log on disk and later compressed into full-database snapshots. One of the main reason new databases are designed as in-memory first is because memory is getting cheaper every year. It is estimated memory is becoming cheaper 40% every year.
MemSQL has tuneable durability. You can make it fully durable or completely ephemeral. It can be sync or async.
MemSQL simplifies your architecture as you don’t have to write ETL jobs to move data from one data store to another data store. This is the biggest selling point of any HTAP database.