Extensible Storage Engine (ESE) is an embedded key-value ISAM DBMS used in various Microsoft products. This system is sometimes referred to as "JET Blue".
ESE was formerly known as Joint Engine Technology (JET) Blue. It was originally developed by Microsoft to replace the JET Red database engine in Access in the 1990s.
Microsoft open-sourced the project in 2021.
N-ary Storage Model (Row/Record)
Indexed Sequential Access Method (ISAM)
Commercial, Open Source