GT.M
GT.M is a high-throughput key–value database engine optimized for transaction processing. (It is a type also referred to as "schema-less", "schema-free", or "NoSQL".) GT.M is also an application development platform and a compiler for the ISO standard M language, also known as MUMPS. GT.M, an abbreviation for Greystone Technology M, was developed by the Greystone Technology Corp in the 1980s.