FoundationDB is really just a set of structures and tools to build any type of database you want on top of a solid foundation. "FoundationDB decouples its data

FoundationDB is really just a set of structures and tools to build any type of database you want on top of a solid foundation. "FoundationDB decouples its data storage technology from its data model. FoundationDB’s core ordered key-value storage technology can be efficiently adapted and remapped to a broad array of rich data models. Using indexing as an example, FoundationDB’s core provides no indexing and never will. Instead, a layer provides indexing by storing two kinds of key-values, one for the data and one for the index." https://apple.github.io/foundationdb/layer-concept.html https://apple.github.io/foundationdb/layer-concept.html Then existing standard layers like the Record layer, providing "(very) roughly equivalent to a simple relational database" providing structured types, index, complex types, queries, etc. https://github.com/FoundationDB/fdb-record-layer https://github.com/FoundationDB/fdb-record-layer Or one for documents, which speaks the MongoDB wire protocol https://github.com/FoundationDB/fdb-document-layer https://github.com/FoundationDB/fdb-document-layer