yeah, MemSQL for me its a combination of RDBMS and NOSQL and more of flexibility of both per our choice, most of the RDBMS going with such concept.
NOSQL is compromise with ACID property and flexible for developers it has its own feature and good stuff and purpose.
MemSQL can be setup per our requirement like can save data on Memory and can be committed later(in-memory), can have redundancy and HA as cluster and replication. it can be used for Analytics as BI. more of an another RDBMS.
I am not a great fever for MemSQL but i am writing this just to be aware that MemSQL existing like other RDBMS.
But Some take it more then this like : Rick Negrin