Linqdb is nosql database for .NET. Chances are it is a much better choice for your project than a relational database.
Server:
Server client:
Embedded:
Read the docs
Linqdb comes as one-process embedded database as well as standalone server with client.
Rocksdb efficiency and easy to use API simillar to Linq queries.
Benchmark
Linqdb is based on Rocksdb which results in great performance characteristics..
Linqdb